Digital BW, The Print

Roy,

Thank you for your well thought out post on Imaging. I refrained from
responding earlier in hopes that someone new would add to your thoughts. As
you mention at the end of your post people are probably a more than a bit
reluctant of even mentioning some of these terms at this point.

I spent some time going through what books I have on photography from a
technical imaging point of view and the concepts that are of concern were
much as you have described them. The spatial component of the system is so
intuitive it is not mentioned except in an artistic manner. What is
discussed at length is the relationship between the SBR (Scene Brightness
Range or Scene Luminosity Range), Density Range and Average Gamma (the
average slope of the line from minimum to maximum which represents
contrast). From these three they map SBR to the film and then to the paper
showing characteristic film and paper curves.

Here in the area of digital printing we still need to define that path from
mapping film density to the print and digital capture opens up similar
questions. With the new technology added to these mappings different
variables may have greater importance at different stages but your 3D
concept holds a great deal of merit in keeping us focused on what is
important.

The idea of distinguishing between tones and the number of tones are
concepts that I do not ever recall hearing in discussions of traditional
photography. If not new concepts, they seem to be new to the discussion of
photography. I believe that they were not discussed in traditional
photography because they simply were of no interest. The technology of
traditional photography generally exceeded the ability of our eyes to
discriminate tones. With the advent of digital imaging, which started out
with quite poor quality, these ideas became vitally important. Once the
quality of the equipment, software and materials of digital imaging
consistently exceeds our eye's ability to discriminate tones the concepts
will once again hold little interest.

Thanks,
Martin Wesley

----- Original Message -----
From: "royvharrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Monday, April 01, 2002 3:02 PM
Subject: [Digital BW] Thoughts about Imaging


>
> Hi All,
>
> The ongoing discussion and debate about dynamic ranges and
> numbers of tones, etc. seems to just go on and on endlessly
> without getting anywhere.  All of us in this group are
> interested in "Imaging" in some form and at some level. I've
> written the following with the idea defining Imaging, seeing
> where the ideas come from, how they relate, how we talk
> and communicate amongst ourselves and others about Imaging.
> Its a little long winded but I felt I need to get my thoughts
> down.
>
> IMAGING
>
> What is Imaging?  I'm talking about anything and everything
> we SEE with our eyes.  Thus X-Ray Imaging, Sonic Imaging are
> all out of the discussion.  Imaging is really DEFINED and
> orginates by and because of human sight.  Our eyes focus
> light from the outside world projecting a 2-dimensional
> imaging on the retina.  The rods and cones of the retina are
> sensitive to light and collect light intensity information
> over a two dimensional space.  The hardware of the eye in
> conjunction with the software of the brain work together to
> give us the perception we call "sight".
>
> An Image is a varying intensity of light spread over a
> two-dimensional space.  Everything in Imaging is related to
> the creation, detection, processing, storage or reproduction
> of Images i.e. varying light over a two-dimension space.
> Certainly, there are many abstractions or intermediate
> representations of Images but they all relate back to the
> original concept of "varying light over a two-dimensional
> space".
>
> Obviously, since "sight" is one of the most basic sense,
> the English language (and I have no doubt all languages) have
> many words relating to "light" and "varying light".  We talk
> about light intensity, brightness, dark/light, black/white.
> A very key issue is that the light intensity varys; we
> are very aware that there is a range of light intensity
> that is "useful".  We can't stare into the bright sun
> because its too intense.  Likewise in a totally dark cave
> we can't see anything.  There is a range of light intensity
> that is humanly useful.  Light intensity can go above or
> below the humanly useful range, but this "useful range" is
> what is interesting.
>
> Putting this all together we have a very good model of
> what an image is.  All told its a 3-dimension object with
> two dimensions that are spacial and one dimension that is
> light intensity.  Another key aspect is that all 3 dimensions
> are "bounded" -- nothing extends out to infinity.  The
> space dimensions are obviously bounded by left and right
> bounds in the horizontal direction and bounded by top and
> bottom in the vertical direction.  The light intensity is
> bounded by "darkest" and "lightest".
>
> Thus, an Image is a 3-dimensional bounded object with two
> spacial dimensions and one light intensity dimension.
>
> As I said earlier, Imaging is everything is related to
> the creation, detection, processing, storage or reproduction
> of Images.  All Imaging operations take an image (3-dim object)
> and at best keep as much information as possible.  In
> reality most will tighten the boundaries some how chopping
> off some of the information.
>
> For a simple example, lets take some photos.  We see a nice image
> and point the camera and look thru the viewfinder.  Immediately
> we've trimmed the two spacial dimensions.  We now have
> much less in view than with our eyes. (Artistically, that's
> probably exactly what we want.)  Next of course we trim
> the light intensity dimension by putting the image on
> film.  The lightest and darkest we can see with our eyes
> is a much wider range than the film in the camera can
> handle.  The film can only record a much narrower range
> of light intensities.  It has a smaller "useful" range.
> Things aren't so bad because although our eyes can handle
> very large ranges of light, often the scene we are
> photographing actually has a much narrower range.  We
> adjust the exposure settings on the camera aligning the
> narrower scene range to narrower film range.  Later on
> when we print the negative we again have the opportunity
> to trim the spacial dimensions (cropping) and of course the
> more challenging task of taking the range of light intensities
> on the film and mapping or transferring them to a piece of
> paper.  The mapping can involve just shifting darker or lighter,
> but also can involve compressing or expanding the range to
> better fit the physical characteristics of different media,
>
> In general, all imaging steps put constraints of some kind
> on the image information.  For an image to go thru many steps
> we've got to be careful at every step of the way.  The end
> result can never be any better than the worst step.  Trimming
> in the spacial dimensions is so obvious that it probably
> needs no discussion, but dealing of the light intensity
> data is probably the main effort in all imaging endeavors.
>
> The set of technologies and industries that an image may
> pass thru from start to finish is truely amazing.  From
> light meters, to exposure, to film, to developing, to
> photo paper, to another developer, toners, etc.  If there's
> digital involved there's CCD's, scanners, A/D and D/A
> converters, lots and lots of computer software, printer
> drivers, printer hardware, paper technology, ink technology.
> Get the idea!
>
> Anyway, every single step of the way deals with the range
> of light intensity.  It's represented in many, many ways,
> but there are several universal characteristics.  First,
> they all have to represent a range of values.  They have
> to have dark values thru light values.  It may be a continuum
> of dark to light or it may be discreet values, but there
> are always endpoints i.e. max and min.  The endpoints
> may be fixed obvious points like white paper and paper
> with the maximum amount of black ink.  Some endpoints are
> a little less obvious -- like film.  Film itself goes from
> fb+f (filmbase+fog) to very, very dense (take film expose
> it to lots of light and develop it a lot), but there is
> definitely a sweet spot -- its linear between the toe and
> the shoulder.  This is the useful range for film.
>
> So in moving the image from one step to the next we need
> to keep moving the range of light values along the road.
> Essentially we want to map the darkest value (and lightest
> value) of one step into the darkest/lightest value of the
> next step.  We are trimming info if that mapping moves
> a value outside the next step's useful range and conversely
> if we don't use the whole range of the new step we are
> using that range to the fullest extent.  One very important
> characteristic is that given two values (darker and lighter)
> they can get closer or farther away tonally. They can even
> merge together so they are no longer distinguishable --
> lost info of course.  But they can never change places.
> This guarantees that mapping max to max and min to min
> keep the range monotonically intact.  We can lose info
> due to merging of tones but sometimes that's unavoidable.
> What is not guaranteed is that the mappings in the middle
> not at all the linear.  Its the linearity and the
> distinguishability in going from one step to the next that
> we spend all our time and effort.
>
> The image with its range of light values moves from step
> to step being subjected to the range of possible values
> for each step.  Each step can represent completely different
> technologies.  In each technology there are whole sets of
> terminology, descriptions and measuring standards for its
> dealing with the range of light values.  The range of
> useful values is called the Dynamic Range.  The Dynamic
> Range describes the range of useful values, but of course
> since the values may be represented in different ways the
> units of expressing the range may vary.  Some technologies
> have very commonly used units and the Range is expressed
> in those units.  Some use the term just descriptively
> to refer to the range but there really isn't a measure
> or quoted number for the dynamic range.
>
> Here's a few examples to show some of the variation.
>
> Dynamic Range of film can be expressed as density range
> of film itself from the minimum to the maximum useful
> density.
> Alternatively, it could be quoted in the number of stops
> of exposure variation that leads to the above densities.
>
> Dynamic Range of a scanner is typically quoted as the
> maximum density of the film that the scanner can  get
> detail from.  Here, minimum density is assumed to be
> zero, so it is a range.
>
> For a final print Dynamic Range is just the white of
> the paper to the max black ink we can get.
>
> A particularly curious case is the data file inside the
> computer.  If its a 8-bit grayscale, by convention 0 is
> black and 255 is white, if it was a bitmap (1-bit) there's
> just 0 and 1.  In a sense they both have the same
> dynamic range but being unitless and totally arbitrary
> it probably not very informative.
>
> The point here it that the term "Dynamic Range" is used
> in many different contexts both as a calculatable measure
> and as a descriptive label for the range.  The key is that
> all the contexts are tied together by the mapping of
> the range of one step onto the range of the next step.
> And the ranges are all ranges of light values from
> dark to light.
>
> --------------------------------------
>
> Obviously, there are other viewpoints about using this
> term "Dynamic Range" (Hi Austin).  But I've looked at quite
> a few specs and discussions using this term, each and
> every one in Imaging uses it in this context.  The range
> of light values from dark to light is unquestionably the
> most basic property of sight.  Austin's Range of Contrasts
> from min contrast to max contrast, leaves me and I believe
> others with a "What the hell is it?" feeling.  I've
> seen several people innocently ask about Dynamic Range
> in a context (I believe) much like my description and barrage
> of discussion that gets nowhere ensues.
> The regulars here now avoid saying the term like they
> avoid the plague.
>
> For me it boils down to two issues:
> 1) Range of Contrasts doesn't help my understanding of
>     Imaging i.e. it doesn't go with a perceptual property
> 2) Nobody else in Imaging uses the term that way.
>
> ---------------------------------------
>
> Term usage aside, I found the exercise of thinking thru
> Imaging to be helpful to myself.  Comments?
>
> Hopefully someone else will find this useful.
>
> Roy
>
> --
> Roy Harrington
> roy@...
> Black & White Photography Gallery
> http://www.harrington.com
>
>
>
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>

> The idea of distinguishing between tones and the number of tones are
> concepts that I do not ever recall hearing in discussions of traditional
> photography. If not new concepts, they seem to be new to the discussion of
> photography. I believe that they were not discussed in traditional
> photography because they simply were of no interest.

Martin,

There WAS life before mailing lists and Internet web sites you know!

That's just so untrue.  I believe it wasn't discussed by "pedestrians", and
given communications as it was until the Internet, there really wasn't a
"general" place TO discuss it.  People didn't meet on a street corner, and
televise their discussion. nor write the discussions up.  But, my point is,
I know personally that I've had this conversation as far back as the mid
70's...with other photography teachers (yes, I taught photography in the mid
70's), students and professionals.  Now that doesn't mean they actually
understood it as dynamic range...but whether you assign a technical name to
a concept or not, the concept still exists, as well as has been discussed
for a LONG time.

I hear photographers talking about the difference between the tonal
gradations of Plus-X and Tri-X somewhat frequently...and how Plus-X looks
"flat" compared to Tri-X...  It isn't density range (as that is defined by
the printing "system), and it isn't tonal "mapping" that causes this (as
that can be re-mapped any way you want)...

I am amazed at how much energy is being put into "fighting" the concept of
dynamic range.  It reminds me of "bokeh" discussions...

Austin

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, April 03, 2002 7:58 AM
Subject: RE: [Digital BW] Thoughts about Imaging


>
> > The idea of distinguishing between tones and the number of tones are
> > concepts that I do not ever recall hearing in discussions of traditional
> > photography. If not new concepts, they seem to be new to the discussion
of
> > photography. I believe that they were not discussed in traditional
> > photography because they simply were of no interest.
>
> Martin,
>
> There WAS life before mailing lists and Internet web sites you know!

Austin,

Yeah. So what is your point?
>
> That's just so untrue.

I don't recall that you were in any of the discussions I was in or know what
books I read, so how would you know? If I could find or recall a reference
in a book or a magazine article or a workshop discussion, I would say so. If
you have something different, then site me a reference.

>  I believe it wasn't discussed by "pedestrians",

Yes we are all pedestrians here plodding along trying to make the best
prints we can from our images. If it is so important, then why did in not
find its way into pedestrian discussions and magazine articles?

> and
> given communications as it was until the Internet, there really wasn't a
> "general" place TO discuss it.

First you chastise me that there was life before the Internet and now you
tell me there could not have been a broad discussion until we had the
Internet! Books, magazines, periodicals, newspapers, etc. gave enough
opportunity to get the concept spread. The Internet just makes it quicker.
Lots of books have been written on the subject and I have looked over the
few I have, and can find no reference to DyR.

>  People didn't meet on a street corner, and
> televise their discussion. nor write the discussions up.  But, my point
is,
> I know personally that I've had this conversation as far back as the mid
> 70's...

Oh I am sure you did.

> with other photography teachers (yes, I taught photography in the mid
> 70's), students and professionals.  Now that doesn't mean they actually
> understood it as dynamic range...

Or did they simply not agree? You seem to equate not agreeing with you to
not understanding you. It also seems that the 70's was rather far along in
the history of photography and seems pretty recent to me. (An occupational
hazard of getting older)

> but whether you assign a technical name to
> a concept or not, the concept still exists, as well as has been discussed
> for a LONG time.

Fine. Now site me some photographic references to support that DyR, as you
use it, was a concept in wide or even narrow use in the making of
photographs.
>
> I hear photographers talking about the difference between the tonal
> gradations of Plus-X and Tri-X somewhat frequently...and how Plus-X looks
> "flat" compared to Tri-X...  It isn't density range (as that is defined by
> the printing "system), and it isn't tonal "mapping" that causes this (as
> that can be re-mapped any way you want)...

Those seem like pretty pedestrian descriptions to me. I guess pedestrian
descriptions are okay when they support your argument and inadmissible when
they don't. Give me a break.

Sounds like they were talking about the gamma of the two films. Besides if
their Plus-X negs looked flat perhaps they didn't develop them properly. I
took a lot of wonder 35mm Plus-X negs and I personally found that the tonal
renditions in prints to be much nicer than Tri-X. By your definition if had
a better DyR since if you take granularity as noise then Plus-X would have
the higher DyR than Tri-X.
>
> I am amazed at how much energy is being put into "fighting" the concept of
> dynamic range.  It reminds me of "bokeh" discussions...

Absolutely no one is fighting the concept of dynamic range, Austin. Some of
us are resisting your attempts to apply an equation to photographic prints
for which you cannot provide a value or a clear description for the key term
noise. A term that seems to have a high probability of being insignificant.
It is just that what you have explained does not appear to be useful in this
particular case. You have not demonstrated that DyR=10log{(Dmax-Dmin)/noise}
of a print medium tells us anything helpful about making prints.

Roy and I have made attempts to look at the situation from some different
angles and to find some fresh perspectives. How about doing the same?

Best,
Martin

Austin,

If this is true, then how did people learn and develop techniques of 
all kinds.

Back in the 60's and 70's we could not wait for the monthly 
Photography Magazines to hit our mailbox. Those camera club meetings 
were also a forum to discuss and advance the state of the art.

No there were no mailing lists or internet for the pedestrian user, 
but there was definitely a very strong and active network.

-Mike

-- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:
> 
> Martin,
> 
> There WAS life before mailing lists and Internet web sites you know!
> 
> That's just so untrue.  I believe it wasn't discussed 
by "pedestrians", and
> given communications as it was until the Internet, there really 
wasn't a
> "general" place TO discuss it.  People didn't meet on a street 
corner, and
> televise their discussion. nor write the discussions up.

> I believe it wasn't discussed by "pedestrians", and
> given communications as it was until the Internet, there really wasn't a
> "general" place TO discuss it.

What about books, magazines and journals?

BTW, this is the first time I've heard Ansel Adams and his ilk referred to
as pedestrian photo technicians...

If your ilk is so much more sophisticated than his, what the heck you doing
using and teaching his petty "pedestrian" system?

> People didn't meet on a street corner, and
> televise their discussion. nor write the discussions up.

Baloney. One could fill your studio with taped and printed discussions of
dynamic range as it relates to prints. They just use the term differently
than you.

Todd

> > I believe it wasn't discussed by "pedestrians", and
> > given communications as it was until the Internet, there really wasn't a
> > "general" place TO discuss it.
>
> What about books, magazines and journals?

Name them.

> BTW, this is the first time I've heard Ansel Adams and his ilk referred to
> as pedestrian photo technicians...

I wasn't referring to AA at all, exactly the opposite.  We have, in the
group here, what, hundreds of people, very few whom are professionals, and
even fewer who are technologically savvy professionals.

There certainly is a crossing over of non-professionals who are more
technically savvy than most professionals...and I wouldn't call them
pedestrians.  For the most part, most photographers are "pedestrian" in
their understanding of technology, few are very technically inclined, most
are somewhat technically inclined.

> > People didn't meet on a street corner, and
> > televise their discussion. nor write the discussions up.
>
> Baloney. One could fill your studio with taped and printed discussions of
> dynamic range as it relates to prints.

What are these "taped and printed discussions of dynamic range as it relates
to prints", aside from discussions posted on a web page, or in news groups
on the Internet?

BTW, I do understand that people have confused the term dynamic range when
they mean density range, for what ever historical reason...probably because
those doing it didn't really know what dynamic range was.  It is very
similar to the misuse of the term resolution when talking about computer
monitors (or digital cameras ;-).

Austin

Mike,

> If this is true, then how did people learn and develop techniques of
> all kinds.

I agree, but this is vastly different than technical discussions about what
dynamic range really is!  Most photographers don't even understand what
depth of FOCUS is...and I doubt it was discussed at these "meetings".  More
like zoom lenses, cameras, meters...sharing of pictures, "techniques" like
comparing Microdol 1:3 vs D-76 1:1...

> No there were no mailing lists or internet for the pedestrian user,
> but there was definitely a very strong and active network.

Yes, BUT...very one directional...

Regards,

Austin

> > > The idea of distinguishing between tones and the number of tones are
> > > concepts that I do not ever recall hearing in discussions of
> traditional
> > > photography. If not new concepts, they seem to be new to the
> discussion
> of
> > > photography. I believe that they were not discussed in traditional
> > > photography because they simply were of no interest.
>
> >
> > That's just so untrue.
>
> I don't recall that you were in any of the discussions I was in
> or know what
> books I read, so how would you know?

Because you weren't there, doesn't mean it wasn't discussed.

> If
> you have something different, then site me a reference.

I defer to Todd for that ;-)

> >  I believe it wasn't discussed by "pedestrians",
>
> Yes we are all pedestrians here plodding along trying to make the best
> prints we can from our images. If it is so important, then why did in not
> find its way into pedestrian discussions and magazine articles?

Pedestrians don't care about MTF and a host of other very technical analysis
issues, that are VERY important (to some people) to the final image.

> > and
> > given communications as it was until the Internet, there really wasn't a
> > "general" place TO discuss it.
>
> First you chastise me

I did not chastise you at all.  I merely stated that we seem to forget the
role that the Internet has played on "information" (right and wrong
information) availability, as well as given us places to discuss this on a
daily/hourly basis.

> ...and now you
> tell me there could not have been a broad discussion until we had the
> Internet!

That is just not what I said at all.  Of course there were discussions, just
not as "accessible" as today.

> Lots of books have been written on the subject and I have looked over the
> few I have, and can find no reference to DyR.

And that means it doesn't exist?  They didn't discuss film grain
molecularity, did they?

> > with other photography teachers (yes, I taught photography in the mid
> > 70's), students and professionals.  Now that doesn't mean they actually
> > understood it as dynamic range...
>
> Or did they simply not agree?

...they just didn't necessarily call "it" dynamic range.  They may have
called it number of tones or tonality or whatever.

> You seem to equate not agreeing with you to
> not understanding you.

Not at all.  Just because someone understood a concept and didn't give a
particular name to that concept/property doesn't have anything to do with
agreement.

> > but whether you assign a technical name to
> > a concept or not, the concept still exists, as well as has been
> discussed
> > for a LONG time.
>
> Fine. Now site me some photographic references to support that DyR, as you
> use it, was a concept in wide or even narrow use in the making of
> photographs.

I am curious why that matters at all, except as yet another off the real
subject ancillary argument.  If no one discussed it, does it mean that it
didn't exist?  Anyway, AA obviously used the term in "The Negative".  Again,
I defer to Todd on providing references.

> > I hear photographers talking about the difference between the tonal
> > gradations of Plus-X and Tri-X somewhat frequently...and how
> Plus-X looks
> > "flat" compared to Tri-X...  It isn't density range (as that is
> defined by
> > the printing "system), and it isn't tonal "mapping" that causes this (as
> > that can be re-mapped any way you want)...
>
> Those seem like pretty pedestrian descriptions to me. I guess pedestrian
> descriptions are okay when they support your argument and
> inadmissible when
> they don't. Give me a break.

If the description uses ambiguous terms, then they need to be
qualified...and any definition, pedestrian or technical can use ambiguous
terms.  It's just that pedestrian definitions of very technical issues tend
to be incomplete, and technical definitions aren't.  I prefer definitions
that are unambiguous and are complete.  I don't care whether they "seem"
pedestrian or not.

> Sounds like they were talking about the gamma of the two films.

tonal mapping is gamma, not density range, and not the "number" of tonal
gradations.

> Besides if
> their Plus-X negs looked flat perhaps they didn't develop them properly. I
> took a lot of wonder 35mm Plus-X negs and I personally found that
> the tonal
> renditions in prints to be much nicer than Tri-X.

Absolutely, but that doesn't mean that to some people, more/better
gradations as in less contrast don't look flat.

> By your
> definition it [Plus-X] had
> a better DyR since if you take granularity as noise then Plus-X would have
> the higher DyR than Tri-X.

Grain is a contributing factor to dynamic range ;-)

> > I am amazed at how much energy is being put into "fighting" the
> concept of
> > dynamic range.  It reminds me of "bokeh" discussions...
>
> Absolutely no one is fighting the concept of dynamic range,

Claiming it is EXACTLY the same thing as DENSITY RANGE, IS fighting it.

> Austin. Some of
> us are resisting your attempts to apply an equation to photographic prints
> for which you cannot provide a value or a clear description for
> the key term
> noise.

If it doesn't have a FIXED value, then it doesn't exist?  BTW, I HAVE
provided a VERY CLEAR description for the key term "smallest discernable
signal", which may or may not be noise.  You just don't like my answer!
And, because my description may or may not be inadequate, or you may or may
not like/understand it, doesn't mean dynamic range isn't a property of film
and prints.  It is, and it doesn't have to be measured to exist.

> A term that seems to have a high probability of being
> insignificant.

Perhaps to you!  I am sure for some people, it is insignificant, but for my
work it is VERY significant, and it shows in my images.  And it is NOT
DENSITY range, it is DYNAMIC range.

> It is just that what you have explained does not appear to be
> useful in this
> particular case.

To you.

> You have not demonstrated that
> DyR=10log{(Dmax-Dmin)/noise}
> of a print medium tells us anything helpful about making prints.

It is not necessary to "run" the equation and come up with an exact number
to understand the concept (and for it to exist), and have it apply to your
work, that is if your work warrants it.  Tonality IS important, very
important to some, and it is NOT described by density range.

Austin

>>> I believe it wasn't discussed by "pedestrians", and
>>> given communications as it was until the Internet, there really wasn't a
>>> "general" place TO discuss it.
>> 
>> What about books, magazines and journals?
> 
> Name them.
> 
>> BTW, this is the first time I've heard Ansel Adams and his ilk referred to
>> as pedestrian photo technicians...
> 
> I wasn't referring to AA at all, exactly the opposite.  We have, in the
> group here, what, hundreds of people, very few whom are professionals, and
> even fewer who are technologically savvy professionals.

But Mike quoted you Ansel's definition of dynamic range from "The Print" ,
which was:

There are three important scales within the total range of exposures that
can be printed. The full range from black to white is represented by Zones 0
to X. Within this range lies the dynamic range, representing the first
useful values above Zone 0 and below Zone X, or Zones I to IX. The range of
zones which convey definite qualities of texture and the recognition of
substance is the textural range from Zones II to VII. (1)

(1) Ansel Adams, The Negative, Little Brown, Nineteenth Printing, 1998.

Looks like he does NOT support your case.
 
> There certainly is a crossing over of non-professionals who are more
> technically savvy than most professionals...and I wouldn't call them
> pedestrians.  For the most part, most photographers are "pedestrian" in
> their understanding of technology, few are very technically inclined, most
> are somewhat technically inclined.

Well, I'm not really interested in the chat of the lists so much as
published documents found through web search engines. But I'm similarly not
interested in the discussions you may have had with some of your cronies of
the '70s - how do we know you guys weren't a bunch of renegade geeks on
acid? 

(just kidding....sort of)
 
>>> People didn't meet on a street corner, and
>>> televise their discussion. nor write the discussions up.
>> 
>> Baloney. One could fill your studio with taped and printed discussions of
>> dynamic range as it relates to prints.
> 
> What are these "taped and printed discussions of dynamic range as it relates
> to prints", aside from discussions posted on a web page, or in news groups
> on the Internet?

Well, you yourself said you had a dozen books on the topic but only the one
without an index might support your claim. BTW, lets just clarify, the
discussion is whether your interpretation of the dynamic range formula,
which you've taken from electrical engineering, is appropriately applied to
a photographic print, which is more physical and chemical in nature.

I have no doubt your interpretation is right on for scanners and audio eq.

here are a couple that appear non-pedestrian to me. Keep in mind if they get
any less pedestrian I probably can't decipher them. ;-)

http://www.image-acquire.com/articles/resscan.shtml

The photographic measures of dMin and dMax are logarithmic, which means that
small numerical differences can be significant. Nearly all scanners can
handle pure white or completely clear film, which means the dMin is 0, so
the dMax and the dynamic range will be the same. (Dynamic range = dMax -
dMin). However, once you get to a dynamic range of 3.2 or 3.4 you have
already exceeded the dynamic range of ink on paper, and it takes an
experienced user to actually get a better printed piece out of an image
scanned with a dynamic range of 3.7, not to mention the need for an
excellent printing facility and staff.

http://www.marginalsoftware.com/Scanner/dynamic_range.htm

Optical Density and Dynamic Range

Tonal values on film are measured in units of optical density.  This
normative scale ranges from zero density (0.0d) to 4.0d -- clear film to
black.  Density is measured on a base 10 log scale, the numbers represent
the tens exponent of the relative density.  A tonal value measured at 2d is
10 times more dense than one measuring 1d.  A one photographic stop
difference in density is about 0.3.  For example, 2.5d is about one stop
greater in density than 2.2d.  In reality, the sensitivity of film ranges
from .3d (fog and film base density) to about 3.7d.  The shorthand for the
minimum and maximum value that can register on a film or device is D-Min and
D-Max.  Of the two, D-Max is the more important because it is indicative of
the ultimate sensitivity of the film or device.

Dynamic range is simply the difference between the minimum and maximum tonal
values that the film can register. The theoretical dynamic range of film is
then 3.7-.3 = 3.4d, or a bit over 11 stops.  In practice, however, the
typical photographer is able to use a fraction of this range.
 
> BTW, I do understand that people have confused the term dynamic range when
> they mean density range, for what ever historical reason...probably because
> those doing it didn't really know what dynamic range was.  It is very
> similar to the misuse of the term resolution when talking about computer
> monitors (or digital cameras ;-).

Yes, but whatever your notion of monitor resolution I'm sure you'd have a
far easier time finding a source to support your interpretation. Is it that
there are less pedestrians who use computers? ;-)

The thing is, much of what you are saying suggests thsi all broke down in
recent years, due to the dilution of the brain pool by pedestrians via the
internet. But the only time I ever do see something that looks like your
interpretation it's with regard to pixels. IOW, I highly doubt that in the
"good old days" they spoke anymore like you about the DyR of a print.

Todd

Austin,

Yes, perhaps in the camera clubs and high school phot classes. But there was
a whole class of photographer that were deeply involved in developing and
researching the state of the art. Papers were published, research was done,
and scientific data was realized.

Perhaps in your circles these things were not discussed. But in reality,
photographers were travelling to Carmel to learn and speak with Ansel and
others. Ask Sexton, ask Gordon Brown, ask Fred Picker, Berenbaum, ask
Camponigro, ask the Westons and the Zakia's. Ask those that were teaching at
RIT, Brooks, and RISD.

In the late 60's we did test Microdol X, the new Polycontrast papers, and
puked at the quality of the zoom lenses which almost no one bought. But, we
were also mixing Potassium Oxalate, Sodium Chlolplatinite, and we were
testing the "Dynammic Range of papers, film and  the effects of chemistry.

With all due respect, you are very wrong in your statements here.

Mike

Austin wrote:

> I agree, but this is vastly different than technical discussions about
what
> dynamic range really is!  Most photographers don't even understand what
> depth of FOCUS is...and I doubt it was discussed at these "meetings".
More
> like zoom lenses, cameras, meters...sharing of pictures, "techniques" like
> comparing Microdol 1:3 vs D-76 1:1...

Hi Martin,

Thanks for replying, I was feeling a little like my post went into a black-hole :).

I think you bring up some very interesting comments about tones, number
of tones and tonality.  Images in the "real world" or "analog world" are 
completely continuous in all 3-dimensions of the Image Model that I talked 
about in the last post. Let me make it clear what I mean by some examples.  
First the spacial dimensions, all points (and there are an infinite
number) between the left boundary and the right boundary exist.
There are no holes.  If you looked at it as a number line, its a solid line;
its not a series of discrete points.  You can't come up with a point in space
between left and right that is illegal or not part of the image. Likewise,
the tonal dimension is also continuous.  All tones are possible.  If you were
to look at a smooth gradation in tones of a sky all tones from the darkest sky 
tone to the lightest sky tone are represented.  If you were to graph light 
intensity you'd get a nice continuous curves -- no discontinuities.

Aside for Quantum Physics affectionatos:
I'm well aware of quantum physics at the nuclear level.
This is way, way, way out of the realm of human perception and
certainly has no place here.  

Now when we get to all of our Imaging Systems lots of things happen.
The real world continuous Image has an infinite amount of information.
Since all three dimension are continuous the some total is infinite.
The saving grace is that human perception, i.e. sight, can in no way 
gather or process and infinite amount of info.  The limiting factor
is the "resolution" of our eyes.  We have discrete rods and cones in
our eyes and relatively poor optics in the lens of our eye.  Fortunately,
our brains have an amazing capability to integrate "light" info
over both time and space amassing much more "sight information" than
the hardware (the eye) seems capable of.

Anyway, precisely because of the human perceptual limitation we
can gear and design the Image Systems to be only as good as necessary.
We only need the output to be sufficient to mimic the perception
of the original image.  The curious thing here is that the reproduced
image can have drastically different information than the original.
The important thing is ONLY that it stimulates the eye and brain
such that the "perception" is as close as possible.

I'd like to illustrate this important point with a short aside to
the workings of color reproduction.  As most of us know visible
light in the real world is a small, continuous, range of 
electromagnetical radiation.  We call it the spectrum from red to
violet.  In a rainbow humans can see this whole spectrum.  Now 
display that whole spectrum on a computer monitor.  We "see" the
same whole spectrum (at least within the gamut of the monitor).
The BIG, BIG difference is that the monitor only puts out three
distinct frequencies of light.  That's why call them RGB (Red,
Green, Blue).  The only thing magic or special about R,G,and B
is that those colors match the sensitivity of the three types
of cone receptors in the eye.  Our perception of color is by the
brain comparing the balance of light intensities of each of the
3 types.  The RGB monitor need only stimulate the 3 cone types in
the correct balance to produce the perception of any color.  The
point is all color imaging that we do: from film to color printers
the entire 3 color system is designed based on the human eye,
not at all trying to reproduce "physics" notion of the color
spectrum.

My major point here is that: Imaging is always based on trying to
reproduce the human perception not trying to reproduce reality.

Back to black and white Images and Imaging.  As I said earlier,
the human eye has quite a few limitations in resolution and optics.
However what we perceive via the processing of the brain is
significantly better.  Integrating over time (we can watch movies)
and space (the eyes are almost constantly moving -- the receptors
pass thru all points in space) our perception is quite continuous.
Our challenge in Imaging is to provide just enough data so that
the brain can perceive a continuous toned image.  In traditional
photography film is an analog medium based on grains of silver.
The grains themselves are discrete, but given sufficient fine
grain and limited enlargement we can perceive continuous tonal
gradations.  In fact even with very coarse grain, enlarged a lot
we see the grain but we can still "feel" a continuous gradation.
I recently saw a Salgado exhibit that had prints up to about
20x30 inches from high speed 35mm film.  The grain was huge but
stand back a few feet and the tonality was beautiful.  Certainly
not lack of tones.

Digital Imaging presents a whole new set of issues.  First the
basic notion of digital is quantizing values, both spacially
and tonally.  We now have the situation of "holes" in our nice
continuous images i.e. discrete information in discrete places.
This may seem inherently a no win situation, but remember all
that really matters is reproducing a "perception" of a continuous
image.  Obviously, how close all that discrete digital data is
determines whether we get a continuous perception.

There's an awful lot of talk and effort about distinguishing
gray tones.  Given our universally common 256 tones of gray, the
effort always seems to be to figure out how to distinguish as 
many as possible.  While this is in general a noble and worthwhile
effort, there's another side of the story that I think is worth
thinking about.  Its good to have distinguishable gray tones but
it is also very important to have indistinguishable tones. By this
I mean there should be tones that are different in an absolute
sense -- a high quality densitometer would see the difference --
but they are humanly indistinguishable.  Why you say?  Well 
consider a very gradual sky gradation, if all the grays in that
gradient are distinguishable we will perceive a step function in
the tones.  Say the tones are grays 140, 141, 142, 143, 144.  We
want any two adjacent tones to be indistinguishable but any tones
separated by 2 or more to be distinguishable. This will produce the
largest number of distinguishable grays and still allow a continuous 
perception. This is probably one motivation for going to 16 bit tonal
representation -- we want to make sure there are indistinguishable
grays. It sure sounds ironic, but with 256 new gray values between
each original gray you're guaranteed to get some indistinguishable!

The other major factor in producing the perception of continuity
is Noise.  I think in general noise is thought of as a detrimental
factor -- we strive to eliminate it or drive it to zero.  In fact
noise is a wonderfully useful tool to improve the perception of
tonal continuity.  Recently someone in this group noticed that when
using a very simple "gradient" tool in Photoshop, they didn't get
a perfectly flat and pure histogram.  You might think it ought to
get a perfect gradient from dark to light, but in fact the folks
at Adobe, in their extensive knowledge of Imaging, know that the
pure gradient actually doesn't look "good".  In variably, there
distinguishable tones adjacent and the result is perceiving bars
in the gradient.  The solution -- add noise.  Amazingly, the
gradient becomes very smooth.  Actually, its the perception 
which is now very smooth.  The point is to use the processing in
the brain to the best advantage.  For anyone with a sky gradient
which is too posterized adding noise can be a tool to help!

Well, that's about it for now.

Regards,
Roy


--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" <mwesley250@e...> wrote:
> Roy,
> 
> Thank you for your well thought out post on Imaging. I refrained from
> responding earlier in hopes that someone new would add to your thoughts. As
> you mention at the end of your post people are probably a more than a bit
> reluctant of even mentioning some of these terms at this point.
> 
> I spent some time going through what books I have on photography from a
> technical imaging point of view and the concepts that are of concern were
> much as you have described them. The spatial component of the system is so
> intuitive it is not mentioned except in an artistic manner. What is
> discussed at length is the relationship between the SBR (Scene Brightness
> Range or Scene Luminosity Range), Density Range and Average Gamma (the
> average slope of the line from minimum to maximum which represents
> contrast). From these three they map SBR to the film and then to the paper
> showing characteristic film and paper curves.
> 
> Here in the area of digital printing we still need to define that path from
> mapping film density to the print and digital capture opens up similar
> questions. With the new technology added to these mappings different
> variables may have greater importance at different stages but your 3D
> concept holds a great deal of merit in keeping us focused on what is
> important.
> 
> The idea of distinguishing between tones and the number of tones are
> concepts that I do not ever recall hearing in discussions of traditional
> photography. If not new concepts, they seem to be new to the discussion of
> photography. I believe that they were not discussed in traditional
> photography because they simply were of no interest. The technology of
> traditional photography generally exceeded the ability of our eyes to
> discriminate tones. With the advent of digital imaging, which started out
> with quite poor quality, these ideas became vitally important. Once the
> quality of the equipment, software and materials of digital imaging
> consistently exceeds our eye's ability to discriminate tones the concepts
> will once again hold little interest.
> 
> Thanks,
> Martin Wesley
> 

Roy Harrington
roy@...
Black & White Photography Gallery
http://www.harrington.com

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> 
> What are these "taped and printed discussions of dynamic range as it relates
> to prints", aside from discussions posted on a web page, or in news groups
> on the Internet?
> 
> BTW, I do understand that people have confused the term dynamic range when
> they mean density range, for what ever historical reason...probably because
> those doing it didn't really know what dynamic range was.  It is very
> similar to the misuse of the term resolution when talking about computer
> monitors (or digital cameras ;-).
> 
> Austin

Austin,

You've pushed you idea on dynamic range for imaging, time and time again.  Many
people have argued with you.  I personally have gone to the library to look at
your reference book by "Higgins".  First of all I'd like to point out that the
formula and the diagrams you have spoken about are under a paragraph
heading:   1.4.1  DYNAMIC RANGE EXAMPLE: ANALOG VS. DIGITAL AUDIO.
The last word AUDIO is key.  You've claim to have 25 years of experience in
AUDIO, fine.   You've claimed to have taken this formula, plugged in density,
and defined dynamic range for imaging.  I tried several times to point out that
it was at least possible to plug in density to the formula in different ways.
You declined to admit that, saying there wasn't any interpretation, mapping,
or logic, involved in going from the audio formula to imaging.  

Well, bottom line is you're mistaken, incorrect, misinformed or whatever you want
to call it.  I don't expect or even recommend that you believe me.  You've got
to investigate, research, and learn more about the Imaging World and figure it
out for yourself.  I'd be glad to help point you in the right direction but you've
got to do it yourself.  

Here's a couple of hints:
The formula in Higgins book is about audio, explicitly showing the waveform
nature of sound.   The signal diagram shows what to measure with a wave.
Imaging is very different, when we talk about light intensity, or film density
there are no waves.  They are direct measured values that can be perceived
as constant values.  Your interpretation has made density into a waveform
property which it is not.

Get away from the audio books, jettison the audio baggage.  Read some imaging
books.  Here's a nice one:
Read World Scanning and Halftones by Blatner, Fleishman and Roth.
 -- page 13  direct quote
  "Dynamic Range" expresses how broad a range of tonal values a scanner can
  capture; this is similar to the photographic measure of "density".
 -- page 14  direct quote
   ... compare bit depth and dynamic range to a staircase: the dynamic range
   describes the height of the staircase and the bit depth describes the
   number of steps from the bottom to the top.
Read Ansel Adams: The Negative
Read the kodak website -- search for dynamic range.

Whether you like it or not dynamic range is well used in imaging and your 
interpretation doesn't agree with the anyone else.   If you really like your function
call it Austin's Cool Range Formula, and I'm sure we'd all be happy to let you
own it.

I am sorry to be harsh about it, but I really think the aruments have
become a disservice to the group.

Regards,
Roy

Thank you, Roy.

-----Original Message-----
From: royvharrington [mailto:roy@...] 
Sent: Wednesday, April 03, 2002 5:14 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Thoughts about Imaging


--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin"
<darkroom@i...> wrote:
> 
> What are these "taped and printed discussions of dynamic range as it 
> relates to prints", aside from discussions posted on a web page, or in

> news groups on the Internet?
> 
> BTW, I do understand that people have confused the term dynamic range 
> when they mean density range, for what ever historical 
> reason...probably because those doing it didn't really know what 
> dynamic range was.  It is very similar to the misuse of the term 
> resolution when talking about computer monitors (or digital cameras 
> ;-).
> 
> Austin

Austin,

You've pushed you idea on dynamic range for imaging, time and time
again.  Many people have argued with you.  I personally have gone to the
library to look at your reference book by "Higgins".  First of all I'd
like to point out that the formula and the diagrams you have spoken
about are under a paragraph
heading:   1.4.1  DYNAMIC RANGE EXAMPLE: ANALOG VS. DIGITAL AUDIO.
The last word AUDIO is key.  You've claim to have 25 years of experience
in
AUDIO, fine.   You've claimed to have taken this formula, plugged in
density,
and defined dynamic range for imaging.  I tried several times to point
out that it was at least possible to plug in density to the formula in
different ways. You declined to admit that, saying there wasn't any
interpretation, mapping, or logic, involved in going from the audio
formula to imaging.  

Well, bottom line is you're mistaken, incorrect, misinformed or whatever
you want to call it.  I don't expect or even recommend that you believe
me.  You've got to investigate, research, and learn more about the
Imaging World and figure it out for yourself.  I'd be glad to help point
you in the right direction but you've got to do it yourself.  

Here's a couple of hints:
The formula in Higgins book is about audio, explicitly showing the
waveform
nature of sound.   The signal diagram shows what to measure with a wave.
Imaging is very different, when we talk about light intensity, or film
density there are no waves.  They are direct measured values that can be
perceived as constant values.  Your interpretation has made density into
a waveform property which it is not.

Get away from the audio books, jettison the audio baggage.  Read some
imaging books.  Here's a nice one: Read World Scanning and Halftones by
Blatner, Fleishman and Roth.
 -- page 13  direct quote
  "Dynamic Range" expresses how broad a range of tonal values a scanner
can
  capture; this is similar to the photographic measure of "density".
 -- page 14  direct quote
   ... compare bit depth and dynamic range to a staircase: the dynamic
range
   describes the height of the staircase and the bit depth describes the
   number of steps from the bottom to the top.
Read Ansel Adams: The Negative
Read the kodak website -- search for dynamic range.

Whether you like it or not dynamic range is well used in imaging and
your 
interpretation doesn't agree with the anyone else.   If you really like
your function
call it Austin's Cool Range Formula, and I'm sure we'd all be happy to
let you own it.

I am sorry to be harsh about it, but I really think the aruments have
become a disservice to the group.

Regards,
Roy




Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:

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"flames."
- Complete your Yahoo profile.
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Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

Thank you Roy,

You make excellent points.

Being neither an electrical engineer nor an expert in sensitometry I am
heistant to debate the issues with Austin. I am sure that he is a very good
engineer, but it is obvious that he is convined that he is right. I think
that we all agree that there are other interpretations than Austin's
regarding Dynamic Range. However, the really great thing about these lists
is the we "can" debate in an open and informative way.

Great thread, but perhaps we should all agree to disagree and go on to the
next issue.

Mike


----- Original Message -----
From: "royvharrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, April 03, 2002 8:14 PM
Subject: Re: [Digital BW] Thoughts about Imaging


> --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin"
<darkroom@i...> wrote:
> >
> > What are these "taped and printed discussions of dynamic range as it
relates
> > to prints", aside from discussions posted on a web page, or in news
groups
> > on the Internet?
> >
> > BTW, I do understand that people have confused the term dynamic range
when
> > they mean density range, for what ever historical reason...probably
because
> > those doing it didn't really know what dynamic range was.  It is very
> > similar to the misuse of the term resolution when talking about computer
> > monitors (or digital cameras ;-).
> >
> > Austin
>
> Austin,
>
> You've pushed you idea on dynamic range for imaging, time and time again.
Many
> people have argued with you.  I personally have gone to the library to
look at
> your reference book by "Higgins".  First of all I'd like to point out that
the
> formula and the diagrams you have spoken about are under a paragraph
> heading:   1.4.1  DYNAMIC RANGE EXAMPLE: ANALOG VS. DIGITAL AUDIO.
> The last word AUDIO is key.  You've claim to have 25 years of experience
in
> AUDIO, fine.   You've claimed to have taken this formula, plugged in
density,
> and defined dynamic range for imaging.  I tried several times to point out
that
> it was at least possible to plug in density to the formula in different
ways.
> You declined to admit that, saying there wasn't any interpretation,
mapping,
> or logic, involved in going from the audio formula to imaging.
>
> Well, bottom line is you're mistaken, incorrect, misinformed or whatever
you want
> to call it.  I don't expect or even recommend that you believe me.  You've
got
> to investigate, research, and learn more about the Imaging World and
figure it
> out for yourself.  I'd be glad to help point you in the right direction
but you've
> got to do it yourself.
>
> Here's a couple of hints:
> The formula in Higgins book is about audio, explicitly showing the
waveform
> nature of sound.   The signal diagram shows what to measure with a wave.
> Imaging is very different, when we talk about light intensity, or film
density
> there are no waves.  They are direct measured values that can be perceived
> as constant values.  Your interpretation has made density into a waveform
> property which it is not.
>
> Get away from the audio books, jettison the audio baggage.  Read some
imaging
> books.  Here's a nice one:
> Read World Scanning and Halftones by Blatner, Fleishman and Roth.
>  -- page 13  direct quote
>   "Dynamic Range" expresses how broad a range of tonal values a scanner
can
>   capture; this is similar to the photographic measure of "density".
>  -- page 14  direct quote
>    ... compare bit depth and dynamic range to a staircase: the dynamic
range
>    describes the height of the staircase and the bit depth describes the
>    number of steps from the bottom to the top.
> Read Ansel Adams: The Negative
> Read the kodak website -- search for dynamic range.
>
> Whether you like it or not dynamic range is well used in imaging and your
> interpretation doesn't agree with the anyone else.   If you really like
your function
> call it Austin's Cool Range Formula, and I'm sure we'd all be happy to let
you
> own it.
>
> I am sorry to be harsh about it, but I really think the aruments have
> become a disservice to the group.
>
> Regards,
> Roy
>
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
> - Include your full name with your message.
> - Include the address of your website, if you have one.
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - As the topic of a thread changes remember to change the subject header.
> - Good manners are required at all time. No personal attacks or "flames."
> - Complete your Yahoo profile.
> - Before posting a question, search the message archives and the various
resources on the homepage.

>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

Richard-

I really enjoyed your previous post on the subject.  It was a well reasoned discussion 
and broadened the perspective of the discussion.  Thanks for the effort.

I do have a couple of points on the comments below.  Austin's formula (and slight 
variations thereof) is used extensively in digital signal processing, and I am famialiar 
with it in that context ( my EE background).  The fomula is valid for signals that are 
not time variant as well as signals that are.  This is a link to some background material 
(not definative but topical). http://www.prosig.com/signal-processing/

Is Austin's definition the only appropriate one?  No.
Do people use dynamic range to mean density range?  Yes
Is that a valid use of the term?  I think so.
Is the formula valid outside of signal processing or describing systems? Not sure.

It seems wrong to leave the impression that Austin's position, although apparently 
intractable, is without merit.

Kevin Gulstene

--- In DigitalBlackandWhiteThePrint@y..., "royvharrington" <roy@h...> wrote:
> --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> 
wrote:
> > 
> > What are these "taped and printed discussions of dynamic range as it relates
> > to prints", aside from discussions posted on a web page, or in news groups
> > on the Internet?
> > 
> > BTW, I do understand that people have confused the term dynamic range when
> > they mean density range, for what ever historical reason...probably because
> > those doing it didn't really know what dynamic range was.  It is very
> > similar to the misuse of the term resolution when talking about computer
> > monitors (or digital cameras ;-).
> > 
> > Austin
> 
> Austin,
> 
> You've pushed you idea on dynamic range for imaging, time and time again.  Many
> people have argued with you.  I personally have gone to the library to look at
> your reference book by "Higgins".  First of all I'd like to point out that the
> formula and the diagrams you have spoken about are under a paragraph
> heading:   1.4.1  DYNAMIC RANGE EXAMPLE: ANALOG VS. DIGITAL AUDIO.
> The last word AUDIO is key.  You've claim to have 25 years of experience in
> AUDIO, fine.   You've claimed to have taken this formula, plugged in density,
> and defined dynamic range for imaging.  I tried several times to point out that
> it was at least possible to plug in density to the formula in different ways.
> You declined to admit that, saying there wasn't any interpretation, mapping,
> or logic, involved in going from the audio formula to imaging.  
> 
> Well, bottom line is you're mistaken, incorrect, misinformed or whatever you 
want

> to call it.  I don't expect or even recommend that you believe me.  You've got
> to investigate, research, and learn more about the Imaging World and figure it
> out for yourself.  I'd be glad to help point you in the right direction but you've
> got to do it yourself.  
> 
> Here's a couple of hints:
> The formula in Higgins book is about audio, explicitly showing the waveform
> nature of sound.   The signal diagram shows what to measure with a wave.
> Imaging is very different, when we talk about light intensity, or film density
> there are no waves.  They are direct measured values that can be perceived
> as constant values.  Your interpretation has made density into a waveform
> property which it is not.
> 
> Get away from the audio books, jettison the audio baggage.  Read some imaging
> books.  Here's a nice one:
> Read World Scanning and Halftones by Blatner, Fleishman and Roth.
>  -- page 13  direct quote
>   "Dynamic Range" expresses how broad a range of tonal values a scanner can
>   capture; this is similar to the photographic measure of "density".
>  -- page 14  direct quote
>    ... compare bit depth and dynamic range to a staircase: the dynamic range
>    describes the height of the staircase and the bit depth describes the
>    number of steps from the bottom to the top.
> Read Ansel Adams: The Negative
> Read the kodak website -- search for dynamic range.
> 
> Whether you like it or not dynamic range is well used in imaging and your 
> interpretation doesn't agree with the anyone else.   If you really like your function
> call it Austin's Cool Range Formula, and I'm sure we'd all be happy to let you
> own it.
> 
> I am sorry to be harsh about it, but I really think the aruments have
> become a disservice to the group.
> 
> Regards,
> Roy

> Do people use dynamic range to mean density range?  Yes
> Is that a valid use of the term?  I think so.

Hi Kevin, thanks for your post.  My question is, if density range and
dynamic range are the same, and we have defined density range as (dMax -
dMin), than what is "dynamic" about it?

Regards,

Austin

Hi Mike,

> Perhaps in your circles these things were not discussed.

I didn't say these things weren't discussed, these things WERE discussed,
but by less people and the discussions had much less exposure (sorry ;-).
The Internet has allowed more people of varying levels of understanding and
expertise TO discuss these things, than has ever been possible.

Regards,

Austin

>
> Austin wrote:
>
> > I agree, but this is vastly different than technical discussions about
> what
> > dynamic range really is!  Most photographers don't even understand what
> > depth of FOCUS is...and I doubt it was discussed at these "meetings".
> More
> > like zoom lenses, cameras, meters...sharing of pictures,
> "techniques" like
> > comparing Microdol 1:3 vs D-76 1:1...

Austin-
I don't know.
<friendly sarcasm on>
There is no cream in my Ice Cream either but I can use the term outside the dairy 
industry and most people know what I mean.
<friendly sarcasm off>

I'm taking Mr. Kravit's advice now and moving on to other topics.

Kevin Gulstene
--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:

> 
> > Do people use dynamic range to mean density range?  Yes
> > Is that a valid use of the term?  I think so.
> 
> Hi Kevin, thanks for your post.  My question is, if density range and
> dynamic range are the same, and we have defined density range as (dMax -
> dMin), than what is "dynamic" about it?
> 
> Regards,
> 
> Austin

Hi Todd,

> But Mike quoted you Ansel's definition of dynamic range from "The Print" ,
> which was:
>
> There are three important scales within the total range of exposures that
> can be printed. The full range from black to white is represented
> by Zones 0
> to X. Within this range lies the dynamic range, representing the first
> useful values above Zone 0 and below Zone X, or Zones I to IX.
> The range of
> zones which convey definite qualities of texture and the recognition of
> substance is the textural range from Zones II to VII. (1)
>
> (1) Ansel Adams, The Negative, Little Brown, Nineteenth Printing, 1998.
>
> Looks like he does NOT support your case.

But in fact it DOES.  He clearly states "the first USEFUL value", which is
exactly the same as "discernable signal".  Also, he is clearly outlining the
DENSITY range as being from 0 to X, and WITHIN THIS range, lies the dynamic
range.  Well, that's entirely true, and completely agrees with what I've
said.  Also, "definite qualities of TEXTURE and the recognition of substance
is the textural range..." means he's simply defining a very coarse DYNAMIC
RANGE!

> Well, I'm not really interested in the chat of the lists so much as
> published documents found through web search engines.

I find there is a LOT of misinformation on the web, unfortunately,
especially on this issue.  No surprise.

> BTW, lets just clarify, the
> discussion is whether your interpretation of the dynamic range formula,
> which you've taken from electrical engineering, is appropriately
> applied to
> a photographic print, which is more physical and chemical in nature.

Hum.  I was only using the definition/example (which is CLEARLY labeled as
an example) from Higgins, not trying to take "a formula from electrical
engineering"...  I look at it as a system property, not an electrical
property, and there are many systems that are not electrical.  Even in
mechanical engineering we used to discuss dynamic range as a viable
property.

> here are a couple that appear non-pedestrian to me.

Yea, like I said, a lot of misinformation seems to proliferate.  Just like
the misuse of resolution with respect to monitor screens...  Sigh.

> Dynamic range is simply the difference between the minimum and
> maximum tonal
> values that the film can register.

Yeah, but it isn't.  What's dynamic about it?  Dynamic means "variation in
force or intensity".  The two static numbers, dMax and dMin, used to define
density range are insufficient to be dynamic.  The changes in tones within
this density range IS dynamic, hence, why it is called dynamic range ;-)

> Yes, but whatever your notion of monitor resolution I'm sure you'd have a
> far easier time finding a source to support your interpretation.

Yeah, that's true, since the definition of resolution is a LOT easier than
the equation/concept of dynamic range ;-)

> The thing is, much of what you are saying suggests thsi all broke down in
> recent years, due to the dilution of the brain pool by pedestrians via the
> internet.

Not at all...I believe it's been a misuse of the term for a long time, but
it's certainly far more prolific because of the Internet.

Regards,

Austin

> Austin-
> I don't know.
> <friendly sarcasm on>
> There is no cream in my Ice Cream either but I can use the term
> outside the dairy
> industry and most people know what I mean.
> <friendly sarcasm off>

He he...kind of like "Grape Nuts", eh?

I know you're going to love this one, but it depends on what definition of
cream you use!  Cream doesn't only mean "the yellowish fatty component of
unhomogenized milk that tends to accumulate at the surface", but "any of
various substances resembling ... cream", and I will say, the mixture is
pretty "creamy"...though I believe there is no ice in it ;-)

Regards,

Austin

Let's not start another long, worthless thread, Austin. I beg of you.
Please.

-----Original Message-----
From: Austin Franklin [mailto:darkroom@...tcom.com] 
Sent: Wednesday, April 03, 2002 7:48 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: RE: [Digital BW] Re: Thoughts about Imaging



> Austin-
> I don't know.
> <friendly sarcasm on>
> There is no cream in my Ice Cream either but I can use the term 
> outside the dairy industry and most people know what I mean.
> <friendly sarcasm off>

He he...kind of like "Grape Nuts", eh?

I know you're going to love this one, but it depends on what definition
of cream you use!  Cream doesn't only mean "the yellowish fatty
component of unhomogenized milk that tends to accumulate at the
surface", but "any of various substances resembling ... cream", and I
will say, the mixture is pretty "creamy"...though I believe there is no
ice in it ;-)

Regards,

Austin



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--- In DigitalBlackandWhiteThePrint@y..., "gulstenek" <kevin@d...> wrote:
> Richard-
> 
> I really enjoyed your previous post on the subject.  It was a well reasoned discussion 
> and broadened the perspective of the discussion.  Thanks for the effort.

I believe you are referring to me.  Thanks for reading it.
BTW, just eliminate confusion its Roy not Richard.

> 
> I do have a couple of points on the comments below.  Austin's formula (and slight 
> variations thereof) is used extensively in digital signal processing, and I am famialiar 
> with it in that context ( my EE background).  The fomula is valid for signals that are 
> not time variant as well as signals that are.  

Absolutely, true.  Imaging is certainly the example here of a non-time varying
signal that is amenable to the "dynamic range" concept.  The thing is you have to
be careful how to translate one system into the other.  Here's another way
to look at the issue that easily works in both systems.

Dynamic Range is a characterization how much bigger the maximum intensity is
from the minimum intensity of the system.  In sound that's the ratio of the loudest
to the quietest.  In an image that's the ratio of the brightest to the darkest.  
Austin's ratio is of the high contrast to the lowest contrast.  It just doesn't jive.

This is a link to some background material 
> (not definative but topical). http://www.prosig.com/signal-processing/

I read thru several articles, very audio oriented.

> 
> Is Austin's definition the only appropriate one?  No.
> Do people use dynamic range to mean density range?  Yes
> Is that a valid use of the term?  I think so.
> Is the formula valid outside of signal processing or describing systems? Not sure.
> 
> It seems wrong to leave the impression that Austin's position, although apparently 
> intractable, is without merit.
> 
> Kevin Gulstene

Roy Harrington

Aack, breaking my vow of silence to say oops, sorry Roy.

I follow your logic.  I can't think of anything to say that hasn't been said though.

<vow of silence back on>

Austin,

I am afraid that I just don't see any point in answering you in detail on
the items below. The trains of thought become so fractured that they lose
all meaning. I do have to take exception to your deleting of portions of the
previous message you are responding to without inserting a "(snip)" or
something similar to indicate you have removed things from their context.

In general I have nothing new to add. Your definition of dynamic range is
correct and completely acceptable to me in the many areas especially
electronics, audio and digital processing. Most importantly for us on this
list in terms of scanning. The concept you present is not being rejected and
is no way in error.

However, to be meaningful your concept is based upon the inclusion of noise
in both the concept and the calculation. In this regard I believe that the
concept you have presented MAY not be of interest in comparing various
combinations of ink/paper or silver papers because the noise in these print
mediums is very low and performing the calculations would leave us comparing
one large number to another. In other words, once the noise becomes so small
that it is no longer observable by the viewer it can be ignored. This is not
to say that it does not exist but may be irrelevant.

If you can demonstrate that the noise in a print medium (I stress here print
medium and not any individual print) is large enough to effect the visual
quality of the prints and produce DyR values that help us compare print
mediums, then I am most interested. As a theoretical debate it no longer
holds any interest for me.

It is also a point of fact that in photography, regardless of your own
opinions on the mater, dynamic range has been understood to be the density
range Dmax-Dmin. I want to stress again to you and to everyone else that
subtracting two log values such as density is an expression of the ratio
between the two properties. This is in complete agreement with the common
definition of dynamic range. I put it to you that the burden is upon you to
show that the more detailed equation of DyR is more applicable and the
burden is not on everyone else to defend a long accepted practice.

I also still contend that the concept that a photographic print has a finite
number of tones between min and max is also an unusual and unfounded idea
outside of a purely digital image as in a scan file. An actual print either
appears to have a continuous, unbroken change from tone to tone or it looks
posterized and inferior in quality. There seems to be very little latitude
at this threshold.

You have used the word tonality and suggested that this is in reference to
the number of tones in a print. This in not a proper usage of the word which
is:

Tonality:
1 : tonal quality
2 a : KEY  b : the organization of all the tones and harmonies of a piece of
music in relation to a tonic
3 : the arrangement or interrelation of the tones of a work of visual art

This is an artistic term and not a technical one and by no stretch of the
imagination implies quantity but simply relationship.

Martin


----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, April 03, 2002 1:07 PM
Subject: RE: [Digital BW] Thoughts about Imaging


> > > > The idea of distinguishing between tones and the number of tones are
> > > > concepts that I do not ever recall hearing in discussions of
> > traditional
> > > > photography. If not new concepts, they seem to be new to the
> > discussion
> > of
> > > > photography. I believe that they were not discussed in traditional
> > > > photography because they simply were of no interest.
> >
> > >
> > > That's just so untrue.
> >
> > I don't recall that you were in any of the discussions I was in
> > or know what
> > books I read, so how would you know?
>
> Because you weren't there, doesn't mean it wasn't discussed.
>
> > If
> > you have something different, then site me a reference.
>
> I defer to Todd for that ;-)
>
> > >  I believe it wasn't discussed by "pedestrians",
> >
> > Yes we are all pedestrians here plodding along trying to make the best
> > prints we can from our images. If it is so important, then why did in
not
> > find its way into pedestrian discussions and magazine articles?
>
> Pedestrians don't care about MTF and a host of other very technical
analysis
> issues, that are VERY important (to some people) to the final image.
>
> > > and
> > > given communications as it was until the Internet, there really wasn't
a
> > > "general" place TO discuss it.
> >
> > First you chastise me
>
> I did not chastise you at all.  I merely stated that we seem to forget the
> role that the Internet has played on "information" (right and wrong
> information) availability, as well as given us places to discuss this on a
> daily/hourly basis.
>
> > ...and now you
> > tell me there could not have been a broad discussion until we had the
> > Internet!
>
> That is just not what I said at all.  Of course there were discussions,
just
> not as "accessible" as today.
>
> > Lots of books have been written on the subject and I have looked over
the
> > few I have, and can find no reference to DyR.
>
> And that means it doesn't exist?  They didn't discuss film grain
> molecularity, did they?
>
> > > with other photography teachers (yes, I taught photography in the mid
> > > 70's), students and professionals.  Now that doesn't mean they
actually
> > > understood it as dynamic range...
> >
> > Or did they simply not agree?
>
> ...they just didn't necessarily call "it" dynamic range.  They may have
> called it number of tones or tonality or whatever.
>
> > You seem to equate not agreeing with you to
> > not understanding you.
>
> Not at all.  Just because someone understood a concept and didn't give a
> particular name to that concept/property doesn't have anything to do with
> agreement.
>
> > > but whether you assign a technical name to
> > > a concept or not, the concept still exists, as well as has been
> > discussed
> > > for a LONG time.
> >
> > Fine. Now site me some photographic references to support that DyR, as
you
> > use it, was a concept in wide or even narrow use in the making of
> > photographs.
>
> I am curious why that matters at all, except as yet another off the real
> subject ancillary argument.  If no one discussed it, does it mean that it
> didn't exist?  Anyway, AA obviously used the term in "The Negative".
Again,
> I defer to Todd on providing references.
>
> > > I hear photographers talking about the difference between the tonal
> > > gradations of Plus-X and Tri-X somewhat frequently...and how
> > Plus-X looks
> > > "flat" compared to Tri-X...  It isn't density range (as that is
> > defined by
> > > the printing "system), and it isn't tonal "mapping" that causes this
(as
> > > that can be re-mapped any way you want)...
> >
> > Those seem like pretty pedestrian descriptions to me. I guess pedestrian
> > descriptions are okay when they support your argument and
> > inadmissible when
> > they don't. Give me a break.
>
> If the description uses ambiguous terms, then they need to be
> qualified...and any definition, pedestrian or technical can use ambiguous
> terms.  It's just that pedestrian definitions of very technical issues
tend
> to be incomplete, and technical definitions aren't.  I prefer definitions
> that are unambiguous and are complete.  I don't care whether they "seem"
> pedestrian or not.
>
> > Sounds like they were talking about the gamma of the two films.
>
> tonal mapping is gamma, not density range, and not the "number" of tonal
> gradations.
>
> > Besides if
> > their Plus-X negs looked flat perhaps they didn't develop them properly.
I
> > took a lot of wonder 35mm Plus-X negs and I personally found that
> > the tonal
> > renditions in prints to be much nicer than Tri-X.
>
> Absolutely, but that doesn't mean that to some people, more/better
> gradations as in less contrast don't look flat.
>
> > By your
> > definition it [Plus-X] had
> > a better DyR since if you take granularity as noise then Plus-X would
have
> > the higher DyR than Tri-X.
>
> Grain is a contributing factor to dynamic range ;-)
>
> > > I am amazed at how much energy is being put into "fighting" the
> > concept of
> > > dynamic range.  It reminds me of "bokeh" discussions...
> >
> > Absolutely no one is fighting the concept of dynamic range,
>
> Claiming it is EXACTLY the same thing as DENSITY RANGE, IS fighting it.
>
> > Austin. Some of
> > us are resisting your attempts to apply an equation to photographic
prints
> > for which you cannot provide a value or a clear description for
> > the key term
> > noise.
>
> If it doesn't have a FIXED value, then it doesn't exist?  BTW, I HAVE
> provided a VERY CLEAR description for the key term "smallest discernable
> signal", which may or may not be noise.  You just don't like my answer!
> And, because my description may or may not be inadequate, or you may or
may
> not like/understand it, doesn't mean dynamic range isn't a property of
film
> and prints.  It is, and it doesn't have to be measured to exist.
>
> > A term that seems to have a high probability of being
> > insignificant.
>
> Perhaps to you!  I am sure for some people, it is insignificant, but for
my
> work it is VERY significant, and it shows in my images.  And it is NOT
> DENSITY range, it is DYNAMIC range.
>
> > It is just that what you have explained does not appear to be
> > useful in this
> > particular case.
>
> To you.
>
> > You have not demonstrated that
> > DyR=10log{(Dmax-Dmin)/noise}
> > of a print medium tells us anything helpful about making prints.
>
> It is not necessary to "run" the equation and come up with an exact number
> to understand the concept (and for it to exist), and have it apply to your
> work, that is if your work warrants it.  Tonality IS important, very
> important to some, and it is NOT described by density range.
>
> Austin
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
> - Include your full name with your message.
> - Include the address of your website, if you have one.
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - As the topic of a thread changes remember to change the subject header.
> - Good manners are required at all time. No personal attacks or "flames."
> - Complete your Yahoo profile.
> - Before posting a question, search the message archives and the various
resources on the homepage.

>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>

Martin,

> The trains of thought become so fractured that they lose
> all meaning.

I know, that's why I like very short posts...but we seem to have a few quite
prolific writers here, with many nits to pick ;-)

> I do have to take exception to your deleting of
> portions of the
> previous message you are responding to without inserting a "(snip)" or
> something similar to indicate you have removed things from their context.

Understood.

> Your definition of dynamic range is
> correct and completely acceptable to me in the many areas especially
> electronics, audio and digital processing. Most importantly for us on this
> list in terms of scanning. The concept you present is not being
> rejected and
> is no way in error.

OK, I can work from there ;-)

> However, to be meaningful your concept is based upon the
> inclusion of noise
> in both the concept and the calculation. In this regard I believe that the
> concept you have presented MAY not be of interest in comparing various
> combinations of ink/paper or silver papers because the noise in
> these print
> mediums is very low and performing the calculations would leave
> us comparing
> one large number to another. In other words, once the noise
> becomes so small
> that it is no longer observable by the viewer it can be ignored.
> This is not
> to say that it does not exist but may be irrelevant.

I understand and appreciate that.

> If you can demonstrate that the noise in a print medium (I stress
> here print
> medium and not any individual print) is large enough to effect the visual
> quality of the prints and produce DyR values that help us compare print
> mediums, then I am most interested. As a theoretical debate it no longer
> holds any interest for me.

When my new lab is set-up, I will be more than happy to spend some time
doing some experiments, and, as expected, posting the methodology and
results for review.

> It is also a point of fact that in photography, regardless of your own
> opinions on the mater, dynamic range has been understood to be the density
> range Dmax-Dmin.

Oh, I do know that to be true.

> This is in complete agreement with the common
> definition of dynamic range.

Well, not with the common definition of dynamic range OUTSIDE of it's (I
believe) misuse in the photographic industry, but within the photographic
industry, I agree.  I didn't say it was correct, but I agree with your
statement.

> I also still contend that the concept that a photographic print
> has a finite
> number of tones between min and max is also an unusual and unfounded idea

Number isn't a good word for this concept, unfortunately.  It's not an exact
number I believe is cared about, but that one can "observe" (by what ever
methodology) an image has more tones than another image, rather than knowing
the exact number.  I'll have to really think about that, as the "number" of
tones will be a range I believe, and not fixed...

<er, snip ;->

> You have used the word tonality and suggested that this is in reference to
> the number of tones in a print. This in not a proper usage of the
> word which
> is:
>
> Tonality:
> 1 : tonal quality
> 2 a : KEY  b : the organization of all the tones and harmonies of
> a piece of
> music in relation to a tonic
> 3 : the arrangement or interrelation of the tones of a work of visual art
>
> This is an artistic term and not a technical one and by no stretch of the
> imagination implies quantity but simply relationship.

#3, interrelation... doesn't?  I'm not so hung up on it being a "number",
but a distinguishable difference in the number, what ever that number may
be.  Given that, I believe #3 works perfectly for me.

Regards,

Austin

> Dynamic Range is a characterization how much bigger the maximum
> intensity is
> from the minimum intensity of the system.

> In sound that's the
> ratio of the loudest
> to the quietest.

So, "bigger" == ratio.  I'm good with that.

But to move on to, what I feel, is quite important:

> In an image that's the ratio of the brightest
> to the darkest.

Hum.  Do you mean the darkest to the brightest when talking about density
values?  I'll fly with that ;-)  Let's use two examples, both with DENSITY
range = 2.0:

dMax = 4.0
dMin = 2.0

This gives 4.0 / 2.0 or a ratio is 2.0

dMax = 3.0
dMin = 1.0

This gives 3.0 / 1.0 or a ratio of 3.0

Note the density range is the same for both (and we agree that density range
is dMax - dMin)....but using your "brightest" and "darkest" qualifications,
the dynamic ranges are entirely different...but the difference in intensity
is exactly the same - 100:1 (a density value of 2 is 10**2, or 100, no
matter what the dMax or dMin is).  That's why using "brightest" and
"darkest" doesn't work for dynamic range.

So, the RATIO of the brightest to the darkest, for two examples of the same
density range, do not yield the same dynamic range...how can that be?  Their
RATIOS are the same!

BUT...if we used the equation I have been using, ((dMax - dMin) / noise),
the dynamic ranges WOULD be the exact same, given the same amount of noise
for each.  Hum.

> Austin's ratio is of the high contrast to the lowest contrast.

Yes, that works for me, thanks, I think that is well put.

> It just doesn't jive.

You're right, it doesn't even boogie ;-)

Austin

on 4/3/02 10:04 PM, Austin Franklin wrote:

> Hi Kevin, thanks for your post.  My question is, if density range and
> dynamic range are the same, and we have defined density range as (dMax -
> dMin), than what is "dynamic" about it?

First flash the paper, or use dilute developer to process, or change
contrast filters, or selenium tone.... then ask again. ;-)

Todd

> > Hi Kevin, thanks for your post.  My question is, if density range and
> > dynamic range are the same, and we have defined density range as (dMax -
> > dMin), than what is "dynamic" about it?
>
> First flash the paper, or use dilute developer to process, or change
> contrast filters, or selenium tone.... then ask again. ;-)

Ah, but Todd, that doesn't necessarily change the DENSITY range ;-)

Austin

on 4/4/02 12:08 AM, Austin Franklin wrote:

>>> Hi Kevin, thanks for your post.  My question is, if density range and
>>> dynamic range are the same, and we have defined density range as (dMax -
>>> dMin), than what is "dynamic" about it?
>> 
>> First flash the paper, or use dilute developer to process, or change
>> contrast filters, or selenium tone.... then ask again. ;-)
> 
> Ah, but Todd, that doesn't necessarily change the DENSITY range ;-)
> 
> Austin
> 

What? Flashing the paper is the only one that wouldn't, all the others would
would likely have an effect on dMax.

Let me add: tea stain. There, now I have one that affects dMin too. ;-)

Todd

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, April 03, 2002 9:03 PM
Subject: RE: [Digital BW] Thoughts about Imaging


(snip)

> Hum.  Do you mean the darkest to the brightest when talking about density
> values?  I'll fly with that ;-)  Let's use two examples, both with DENSITY
> range = 2.0:
>
> dMax = 4.0
> dMin = 2.0
>
> This gives 4.0 / 2.0 or a ratio is 2.0
>
> dMax = 3.0
> dMin = 1.0
>
> This gives 3.0 / 1.0 or a ratio of 3.0
>
> Note the density range is the same for both (and we agree that density
range
> is dMax - dMin)....but using your "brightest" and "darkest"
qualifications,
> the dynamic ranges are entirely different...but the difference in
intensity
> is exactly the same - 100:1 (a density value of 2 is 10**2, or 100, no
> matter what the dMax or dMin is).  That's why using "brightest" and
> "darkest" doesn't work for dynamic range.
>
> So, the RATIO of the brightest to the darkest, for two examples of the
same
> density range, do not yield the same dynamic range...how can that be?
Their
> RATIOS are the same!
>
> BUT...if we used the equation I have been using, ((dMax - dMin) / noise),
> the dynamic ranges WOULD be the exact same, given the same amount of noise
> for each.  Hum.

Austin,

Once again the confusion over logs and Density as a derived log value from
Reflectance. To determine the "darkest" to "brightest" ratio you have to
subtract Dmin from Dmax to get a representation of the ratio of Rmax divided
by Rmin.

dMax = 4.0 gives you a reflectance of 1/(10^4) = 0.01%
dMin = 2.0 gives 1%
A ratio of 100:1

dMax = 3.0 gives 0.1%
dMin = 1.0 gives 10%
A ratio of 100:1

For both cases the ratio of the Reflectance is 100 so the ratio of
Reflectance would fit your dynamic range criteria of being the same for both
cases.

Does that boogie?

Martin

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> > Dynamic Range is a characterization how much bigger the maximum
> > intensity is
> > from the minimum intensity of the system.
> 
> > In sound that's the
> > ratio of the loudest
> > to the quietest.
> 
> So, "bigger" == ratio.  I'm good with that.
> 
> But to move on to, what I feel, is quite important:
> 
> > In an image that's the ratio of the brightest
> > to the darkest.
> 
> Hum.  Do you mean the darkest to the brightest when talking about density
> values?  I'll fly with that ;-)  Let's use two examples, both with DENSITY
> range = 2.0:
> 
> dMax = 4.0
> dMin = 2.0
> 
> This gives 4.0 / 2.0 or a ratio is 2.0
> 
> dMax = 3.0
> dMin = 1.0
> 
> This gives 3.0 / 1.0 or a ratio of 3.0
> 

Austin, we actually have a potential for making some progress here.
The density numbers quoted are actually LOG density.
So dMax = log10 (max density)   and  dMin = log10 (min density)
Turning these around we have:
    max density = 10^dMax
    min density = 10^dMin

So the actual ratios are:
   10^4.0 / 10^2.0 = 100
   10^3.0 / 10^1.0 = 100

So they are exactly the same.  The fact that people by convention automatically
take the log is just that, convention.

> Note the density range is the same for both (and we agree that density range
> is dMax - dMin)....but using your "brightest" and "darkest" qualifications,
> the dynamic ranges are entirely different...but the difference in intensity
> is exactly the same - 100:1 (a density value of 2 is 10**2, or 100, no
> matter what the dMax or dMin is).  That's why using "brightest" and
> "darkest" doesn't work for dynamic range.

I've made an effort to use words (but of course they are just English) that
show the parallelism.  I've used the work "intensity" since it seems usable in
both sound and light.  "Density" causes some confusion because, first, it is always
quoted with the "log" builtin and, second, density and intensity are inverses.
High density gives low intensity and vice versa.  Another term that could be
used equivalently is the "Energy" ratio.   Energy is a real scientific quantity
that should be easier to nail down.  With audio the ratio is caller a Power ratio
since audio is a time function : Power = Energy / Time.  

> 
> So, the RATIO of the brightest to the darkest, for two examples of the same
> density range, do not yield the same dynamic range...how can that be?  Their
> RATIOS are the same!
> 
> BUT...if we used the equation I have been using, ((dMax - dMin) / noise),
> the dynamic ranges WOULD be the exact same, given the same amount of noise
> for each.  Hum.
> 
> > Austin's ratio is of the high contrast to the lowest contrast.

I really don't have a problem with you calculating this.  The problem is you
want to call it Dynamic Range of Imaging and ALL and I do mean ALL others
in the Imaging world use this particular term with the ratio of brightest
to darkest.  I just don't think there's any sense bucking the world.

> 
> Yes, that works for me, thanks, I think that is well put.
> 
> > It just doesn't jive.
> 
> You're right, it doesn't even boogie ;-)
> 
> Austin

Roy

> It seems wrong to leave the impression that Austin's position, although
> apparently intractable, is without merit.

I don't think any of us believe Austin's notion is without merit, it's just
that he hasn't demonstrated that anybody but him thinks it's worthy of
pursuing WRT prints. I don't mean that to sound too cynical, I just mean he
makes some sense, but it doesn't help his case that he hasn't provided
evidence to support his notion that the DyR formula is meaningful in this
context. "Noise" in analog photography is typically from grain, but silver
papers don't really have a visible grain to speak of, so we don't know what
Austin refers to when he states his formula.

However, there are things that can affect the "tonality", or tonal
distribution, of a print - flashing was one previous example - and having a
neat little formula for expressing those qualities might be useful, though I
doubt it. We speak of the shape of a paper's characteristic curve, hard or
soft tonality, creamy tones, soot and chalk tones. These are some of the
characteristics I thing Austin is thinking of when he speaks to a prints
dynamic range, but the question is, can you ascertain those qualities from
[(dMax-dMin)/noise]? If I tell you one paper has a dynamic range of 2.2 and
another 2.8 do you really envision them any other way than that one has a
greater density range than the other?

Ultimately it's not a question of could you apply Austin's formula, it's
would you?

I find it interesting that for all DyR's reputed relevance to photography,
even Photoshop doesn't include a DyR analysis of a file. Why? I believe one
reason is because it can't know what a file's input values were supposed to
be, and thus can not determine what in the file is "noise". Instead
Photoshop does a far more complex analysis of a file, quantifying every
pixel, and expresses those results in terms you find in the histogram such
as Mean, Standard Deviation, Percentile, etc, - but no DyR. My only point is
that it would seem that DyR, while very useful in some applications, is out
of place in others. I would guess it's out of place where noise is not a
known, or relevant, quantity or quality.

When Austin defines "noise" WRT photo paper, demonstrates that typical photo
papers contain noise to a significant degree, and shows that someone of
repute - other than himself, ;-) - has applied his formula to a print and
gotten meaningful info from it, he may well win all of us over.

I'm kinda rooting for him, as I'm sure many of us are, but he's not there
yet... ;-)

Todd

Hi Todd,

I don't mean to single you out, in fact I think this flavor of response is
felt by several people.

I got myself into the middle of this mess more from a philosophical 
point of view than a technical one.  It seemed at the beginning most of
the discussion was at the technical level so I joined at that level.
Unfortunately, the technical level of different people just varies too much
to get a feeling of consensis. 

To me it boils down to this.  Imaging has been around in many forms for a
long, long time.  I'm talking decades to a century.  Our group here is a small
niche of  the whole Imaging world history.  We may be significant to inkjet
quadtone printing but we all use significant other parts of Imaging.
The notion, the term, the usage of "dynamic range" has been a part of
imaging way beyond just our group's influence.  It's had a very consistent
meaning describing the "useful range of light values" in whatever terms that
are appropriate for a particular imaging technology.  (I guess you could
dispute my claim, but at least come up with at least one example).

So, how can we here is our niche, talk about coming up with a new idea,
new concept of what "dynamic range" means?   We a just a part of a large
community of imaging that long time ago has defined and has commonly used 
this term to mean sometime very specific.  Even contemplating having our
very own "dynamic range" concept that differs from the rest of the world
just seems totally crazy to me.  It doesn't matter how good the idea is,
I just can't imagine how it makes sense to use an existing term.  We have
to talk to other people, use other technologies, read specs, you name it.
Let's make it easy to communicate with the outside world!

Best regards,
Roy


--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:

> 
> 
> > It seems wrong to leave the impression that Austin's position, although
> > apparently intractable, is without merit.
> 
> I don't think any of us believe Austin's notion is without merit, it's just
> that he hasn't demonstrated that anybody but him thinks it's worthy of
> pursuing WRT prints. I don't mean that to sound too cynical, I just mean he
> makes some sense, but it doesn't help his case that he hasn't provided
> evidence to support his notion that the DyR formula is meaningful in this
> context. "Noise" in analog photography is typically from grain, but silver
> papers don't really have a visible grain to speak of, so we don't know what
> Austin refers to when he states his formula.
> 
> However, there are things that can affect the "tonality", or tonal
> distribution, of a print - flashing was one previous example - and having a
> neat little formula for expressing those qualities might be useful, though I
> doubt it. We speak of the shape of a paper's characteristic curve, hard or
> soft tonality, creamy tones, soot and chalk tones. These are some of the
> characteristics I thing Austin is thinking of when he speaks to a prints
> dynamic range, but the question is, can you ascertain those qualities from
> [(dMax-dMin)/noise]? If I tell you one paper has a dynamic range of 2.2 and
> another 2.8 do you really envision them any other way than that one has a
> greater density range than the other?
> 
> Ultimately it's not a question of could you apply Austin's formula, it's
> would you?
> 
> I find it interesting that for all DyR's reputed relevance to photography,
> even Photoshop doesn't include a DyR analysis of a file. Why? I believe one
> reason is because it can't know what a file's input values were supposed to
> be, and thus can not determine what in the file is "noise". Instead
> Photoshop does a far more complex analysis of a file, quantifying every
> pixel, and expresses those results in terms you find in the histogram such
> as Mean, Standard Deviation, Percentile, etc, - but no DyR. My only point is
> that it would seem that DyR, while very useful in some applications, is out
> of place in others. I would guess it's out of place where noise is not a
> known, or relevant, quantity or quality.
> 
> When Austin defines "noise" WRT photo paper, demonstrates that typical photo
> papers contain noise to a significant degree, and shows that someone of
> repute - other than himself, ;-) - has applied his formula to a print and
> gotten meaningful info from it, he may well win all of us over.
> 
> I'm kinda rooting for him, as I'm sure many of us are, but he's not there
> yet... ;-)
> 
> Todd

Roy,

Just to be clear, I'm not advocating that we change the definition of
dynamic range as it relates to photography. On the contrary, Austin has
maintained that his interpretation of it has been in common use up until the
internet became popular (which is what, 8-12 years?) So, I've been
explaining why I don't think it was ever used that way WRT prints (for
reasons of non-linearity, minimal noise, and other logical reasons as I see
them.) However, while some of us can sense something is amiss we don't have
the confidence of conviction to say "I KNOW this to be true", or "I KNOW
that to be false".

Furthermore, I happen to like and respect Austin, and whenever I've
discounted him in the past he's proven me wrong, so I give him room to do so
again. I simply laid out some conditions, which if met, might begin to
rattle my convictions. Some people have accused Austin of being intractable
on the issue and I'm trying not to be that too.

Todd

> 
> Hi Todd,
> 
> I don't mean to single you out, in fact I think this flavor of response is
> felt by several people.
> 
> I got myself into the middle of this mess more from a philosophical
> point of view than a technical one.  It seemed at the beginning most of
> the discussion was at the technical level so I joined at that level.
> Unfortunately, the technical level of different people just varies too much
> to get a feeling of consensis.
> 
> To me it boils down to this.  Imaging has been around in many forms for a
> long, long time.  I'm talking decades to a century.  Our group here is a small
> niche of  the whole Imaging world history.  We may be significant to inkjet
> quadtone printing but we all use significant other parts of Imaging.
> The notion, the term, the usage of "dynamic range" has been a part of
> imaging way beyond just our group's influence.  It's had a very consistent
> meaning describing the "useful range of light values" in whatever terms that
> are appropriate for a particular imaging technology.  (I guess you could
> dispute my claim, but at least come up with at least one example).
> 
> So, how can we here is our niche, talk about coming up with a new idea,
> new concept of what "dynamic range" means?   We a just a part of a large
> community of imaging that long time ago has defined and has commonly used
> this term to mean sometime very specific.  Even contemplating having our
> very own "dynamic range" concept that differs from the rest of the world
> just seems totally crazy to me.  It doesn't matter how good the idea is,
> I just can't imagine how it makes sense to use an existing term.  We have
> to talk to other people, use other technologies, read specs, you name it.
> Let's make it easy to communicate with the outside world!
> 
> Best regards,
> Roy
> 
> 
> --- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:
>> 
>> 
>>> It seems wrong to leave the impression that Austin's position, although
>>> apparently intractable, is without merit.
>> 
>> I don't think any of us believe Austin's notion is without merit, it's just
>> that he hasn't demonstrated that anybody but him thinks it's worthy of
>> pursuing WRT prints. I don't mean that to sound too cynical, I just mean he
>> makes some sense, but it doesn't help his case that he hasn't provided
>> evidence to support his notion that the DyR formula is meaningful in this
>> context. "Noise" in analog photography is typically from grain, but silver
>> papers don't really have a visible grain to speak of, so we don't know what
>> Austin refers to when he states his formula.
>> 
>> However, there are things that can affect the "tonality", or tonal
>> distribution, of a print - flashing was one previous example - and having a
>> neat little formula for expressing those qualities might be useful, though I
>> doubt it. We speak of the shape of a paper's characteristic curve, hard or
>> soft tonality, creamy tones, soot and chalk tones. These are some of the
>> characteristics I thing Austin is thinking of when he speaks to a prints
>> dynamic range, but the question is, can you ascertain those qualities from
>> [(dMax-dMin)/noise]? If I tell you one paper has a dynamic range of 2.2 and
>> another 2.8 do you really envision them any other way than that one has a
>> greater density range than the other?
>> 
>> Ultimately it's not a question of could you apply Austin's formula, it's
>> would you?
>> 
>> I find it interesting that for all DyR's reputed relevance to photography,
>> even Photoshop doesn't include a DyR analysis of a file. Why? I believe one
>> reason is because it can't know what a file's input values were supposed to
>> be, and thus can not determine what in the file is "noise". Instead
>> Photoshop does a far more complex analysis of a file, quantifying every
>> pixel, and expresses those results in terms you find in the histogram such
>> as Mean, Standard Deviation, Percentile, etc, - but no DyR. My only point is
>> that it would seem that DyR, while very useful in some applications, is out
>> of place in others. I would guess it's out of place where noise is not a
>> known, or relevant, quantity or quality.
>> 
>> When Austin defines "noise" WRT photo paper, demonstrates that typical photo
>> papers contain noise to a significant degree, and shows that someone of
>> repute - other than himself, ;-) - has applied his formula to a print and
>> gotten meaningful info from it, he may well win all of us over.
>> 
>> I'm kinda rooting for him, as I'm sure many of us are, but he's not there
>> yet... ;-)
>> 
>> Todd
> 
> 
> 
> 
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>

--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:
> Roy,
> 
> Just to be clear, I'm not advocating that we change the definition of
> dynamic range as it relates to photography. 

Todd,

I figure nobody really, intentionally advocates that.   But we are all talking here
like its a concept that is yet to be decided.  

On the contrary, Austin has
> maintained that his interpretation of it has been in common use up until the
> internet became popular (which is what, 8-12 years?) 

It sure would be nice if he would provide SOME external information that
wasn't audio related.  He's indicated that his background is audio, and the one
reference book is audio.  The audio/imaging transformation is non-trivial,  you
do have to think about it.   If "Austin maintained that his interpretation of it has 
been in common use",  means audio use is that sufficient?  I'd sure like to
see some reference that even hinted at his interpretation.


So, I've been
> explaining why I don't think it was ever used that way WRT prints (for
> reasons of non-linearity, minimal noise, and other logical reasons as I see
> them.) However, while some of us can sense something is amiss we don't have
> the confidence of conviction to say "I KNOW this to be true", or "I KNOW
> that to be false".

Certainly, the  "I KNOW vs YOU KNOW" is a problem -- it doesn't get anywhere.
I've made an effort to get external info.  I've been glancing thru a lot of books
lately just to see how they use "dynamic range" -- many use it without defining it.
With these the best you can do is see if your concept is consistent.
However, I've cited two books that explicitly define it.  First, "The Negative" by
Ansel Adams talks quite definitely about dynamic range.  He even has a nice
diagram showing what he means.   This was written at least two decades ago.
(He's been dead nearly that long).  Second, "Real World Scanning and Halftones"
by Blatner, etc.  has the very clear staircase analogy I cited before.  Obviously,
the common scanner hasn't been around all that long so its not old.  BTW,
this book is the best technical book I have seen in a very long time -- very
worthwhile -- at least to me.

> 
> Furthermore, I happen to like and respect Austin, and whenever I've
> discounted him in the past he's proven me wrong, so I give him room to do so
> again. I simply laid out some conditions, which if met, might begin to
> rattle my convictions. Some people have accused Austin of being intractable
> on the issue and I'm trying not to be that too.

Certainly, everyone ought to have their chance.  I think it behooves anyone
making a stance to also understand the other side.  I made an effort to study
his reference, study what he derived from it, and see where we disagreed.
I found external references that supported my contention.  He ought to
do the same.

I, also, am getting tired of this.  Over the years, I've seen too many of these
unending discussions.  I thought MAYBE I could jump in, make a contribution
that would help defuse this particular one.  Maybe I was wrong.  As you
might guess I'm quite sure of my stance, but that in itself doesn't make
anyone else sure of it.  I have a feeling we just have to ban the
term (dare I say it?) "dynamic range" :-( 

Dynamic regards,
Roy

> 
> Todd
> 
> > 
> > Hi Todd,
> > 
> > I don't mean to single you out, in fact I think this flavor of response is
> > felt by several people.
> > 
> > I got myself into the middle of this mess more from a philosophical
> > point of view than a technical one.  It seemed at the beginning most of
> > the discussion was at the technical level so I joined at that level.
> > Unfortunately, the technical level of different people just varies too much
> > to get a feeling of consensis.
> > 
> > To me it boils down to this.  Imaging has been around in many forms for a
> > long, long time.  I'm talking decades to a century.  Our group here is a small
> > niche of  the whole Imaging world history.  We may be significant to inkjet
> > quadtone printing but we all use significant other parts of Imaging.
> > The notion, the term, the usage of "dynamic range" has been a part of
> > imaging way beyond just our group's influence.  It's had a very consistent
> > meaning describing the "useful range of light values" in whatever terms that
> > are appropriate for a particular imaging technology.  (I guess you could
> > dispute my claim, but at least come up with at least one example).
> > 
> > So, how can we here is our niche, talk about coming up with a new idea,
> > new concept of what "dynamic range" means?   We a just a part of a large
> > community of imaging that long time ago has defined and has commonly used
> > this term to mean sometime very specific.  Even contemplating having our
> > very own "dynamic range" concept that differs from the rest of the world
> > just seems totally crazy to me.  It doesn't matter how good the idea is,
> > I just can't imagine how it makes sense to use an existing term.  We have
> > to talk to other people, use other technologies, read specs, you name it.
> > Let's make it easy to communicate with the outside world!
> > 
> > Best regards,
> > Roy
> >

Roy,

How frustrated any of us are with this thread depends on what we are trying
to get out of it. I sense most people who participated in it go hot and cold
on it, and ultimately feel guilty for letting it go on so long. I know I've
found myself at all points on that spectrum.

However, even though we never found unanimity it doesn't mean we all didn't
learn from it. The reason I'd stay with it even longer (Ya, I hear the
groans) is because underlying the contentious aspect of it is a search to
describe much of what we are looking for in a print; working towards or
against in our work; and a means to communicate about it.

So yes, we got into an issue of definition, formula, and semantics, but
underlying it all was a search for a means to describe something as simple
as the difference between one frame of Tri-x which is properly exposed and
developed, vs one overexposed, overdeveloped, with blown highlights, and
seeing if there isn't (or hasn't been all along) a shorthand yet meaningful
way to describe the tonal difference between the two.

If that conversation is too tedious for some, or irrelevant, or unworthy, or
we don't like the style of some of the participants, so be it, but I
respectfully disagree, and sometimes I'm just willing to walk over coals to
have such a conversation. Guess I'm just one of them renegade geeks on acid.
;-)

Todd 

> --- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:
>> Roy,
>> 
>> Just to be clear, I'm not advocating that we change the definition of
>> dynamic range as it relates to photography.
> 
> Todd,
> 
> I figure nobody really, intentionally advocates that.   But we are all talking
> here
> like its a concept that is yet to be decided.
> 
> On the contrary, Austin has
>> maintained that his interpretation of it has been in common use up until the
>> internet became popular (which is what, 8-12 years?)
> 
> It sure would be nice if he would provide SOME external information that
> wasn't audio related.  He's indicated that his background is audio, and the
> one
> reference book is audio.  The audio/imaging transformation is non-trivial,
> you
> do have to think about it.   If "Austin maintained that his interpretation of
> it has 
> been in common use",  means audio use is that sufficient?  I'd sure like to
> see some reference that even hinted at his interpretation.
> 
> 
> So, I've been
>> explaining why I don't think it was ever used that way WRT prints (for
>> reasons of non-linearity, minimal noise, and other logical reasons as I see
>> them.) However, while some of us can sense something is amiss we don't have
>> the confidence of conviction to say "I KNOW this to be true", or "I KNOW
>> that to be false".
> 
> Certainly, the  "I KNOW vs YOU KNOW" is a problem -- it doesn't get anywhere.
> I've made an effort to get external info.  I've been glancing thru a lot of
> books
> lately just to see how they use "dynamic range" -- many use it without
> defining it.
> With these the best you can do is see if your concept is consistent.
> However, I've cited two books that explicitly define it.  First, "The
> Negative" by
> Ansel Adams talks quite definitely about dynamic range.  He even has a nice
> diagram showing what he means.   This was written at least two decades ago.
> (He's been dead nearly that long).  Second, "Real World Scanning and
> Halftones"
> by Blatner, etc.  has the very clear staircase analogy I cited before.
> Obviously,
> the common scanner hasn't been around all that long so its not old.  BTW,
> this book is the best technical book I have seen in a very long time -- very
> worthwhile -- at least to me.
> 
>> 
>> Furthermore, I happen to like and respect Austin, and whenever I've
>> discounted him in the past he's proven me wrong, so I give him room to do so
>> again. I simply laid out some conditions, which if met, might begin to
>> rattle my convictions. Some people have accused Austin of being intractable
>> on the issue and I'm trying not to be that too.
> 
> Certainly, everyone ought to have their chance.  I think it behooves anyone
> making a stance to also understand the other side.  I made an effort to study
> his reference, study what he derived from it, and see where we disagreed.
> I found external references that supported my contention.  He ought to
> do the same.
> 
> I, also, am getting tired of this.  Over the years, I've seen too many of
> these
> unending discussions.  I thought MAYBE I could jump in, make a contribution
> that would help defuse this particular one.  Maybe I was wrong.  As you
> might guess I'm quite sure of my stance, but that in itself doesn't make
> anyone else sure of it.  I have a feeling we just have to ban the
> term (dare I say it?) "dynamic range" :-(
> 
> Dynamic regards,
> Roy
> 
>> 
>> Todd
>> 
>>> 
>>> Hi Todd,
>>> 
>>> I don't mean to single you out, in fact I think this flavor of response is
>>> felt by several people.
>>> 
>>> I got myself into the middle of this mess more from a philosophical
>>> point of view than a technical one.  It seemed at the beginning most of
>>> the discussion was at the technical level so I joined at that level.
>>> Unfortunately, the technical level of different people just varies too much
>>> to get a feeling of consensis.
>>> 
>>> To me it boils down to this.  Imaging has been around in many forms for a
>>> long, long time.  I'm talking decades to a century.  Our group here is a
>>> small
>>> niche of  the whole Imaging world history.  We may be significant to inkjet
>>> quadtone printing but we all use significant other parts of Imaging.
>>> The notion, the term, the usage of "dynamic range" has been a part of
>>> imaging way beyond just our group's influence.  It's had a very consistent
>>> meaning describing the "useful range of light values" in whatever terms that
>>> are appropriate for a particular imaging technology.  (I guess you could
>>> dispute my claim, but at least come up with at least one example).
>>> 
>>> So, how can we here is our niche, talk about coming up with a new idea,
>>> new concept of what "dynamic range" means?   We a just a part of a large
>>> community of imaging that long time ago has defined and has commonly used
>>> this term to mean sometime very specific.  Even contemplating having our
>>> very own "dynamic range" concept that differs from the rest of the world
>>> just seems totally crazy to me.  It doesn't matter how good the idea is,
>>> I just can't imagine how it makes sense to use an existing term.  We have
>>> to talk to other people, use other technologies, read specs, you name it.
>>> Let's make it easy to communicate with the outside world!
>>> 
>>> Best regards,
>>> Roy

Roy,

> So, how can we here is our niche, talk about coming up with a new idea,
> new concept of what "dynamic range" means?

No one is coming up with any new concepts...  "We" are merely pointing out
that the term has been "misapplied" in this "field", and that it attributes
a different property than, though is loosely related to, density range.

> We a just a part of a large
> community of imaging that long time ago has defined and has commonly used
> this term to mean sometime very specific.

Can you show evidence of this?

> Even contemplating having our
> very own "dynamic range" concept that differs from the rest of the world
> just seems totally crazy to me.

Yeah, just like monitors are talked about in terms of "resolution", which
means something completely different from the use of resolution to the rest
of the world in every other application that uses that term.   Hum.

> It doesn't matter how good the idea is,
> I just can't imagine how it makes sense to use an existing term.  We have
> to talk to other people, use other technologies, read specs, you name it.
> Let's make it easy to communicate with the outside world!

Agreed, but that doesn't mean the term isn't being misused ;-)

Austin

Hi Roy,

> On the contrary, Austin has
> > maintained that his interpretation of it has been in common use
> up until the
> > internet became popular (which is what, 8-12 years?)

Not really.  I maintain that the Internet hasn't helped misuses and
misunderstanding of a lot of things...  I believe the term dynamic range was
misused in this "field" long before the Internet.

> He's indicated that his background is
> audio,

I do have A background in audio, but my "major" background is in imaging (as
well as mobile robotics/Artificial Intelligence).

> and the one
> reference book is audio.

Actually, it's a digital signal processing reference book...and the EXAMPLE
used was audio.

> First,
> "The Negative" by
> Ansel Adams talks quite definitely about dynamic range.

Yes, and I believe, what was quoted at least, does agree with what I have
said.  You obviously interpret the same words differently ;-)  We can
discuss this further if you like.

> Second, "Real World Scanning
> and Halftones"
> by Blatner, etc.

And...the description of dynamic range in that book completely agrees with
my stated definition:

"dynamic range describes the actual limits of how many tones the scanner can
really differentiate from light to dark".

Austin

Hi Todd,

> However, even though we never found unanimity it doesn't mean we
> all didn't
> learn from it.

Agreed.

> The reason I'd stay with it even longer (Ya, I hear the
> groans) is because underlying the contentious aspect of it is a search to
> describe much of what we are looking for in a print; working towards or
> against in our work; and a means to communicate about it.

Which is EXACTLY why I believe dynamic range is an important
concept/property to understand and distinguish from density range.

Regards,

Austin

> > Second, "Real World Scanning
> > and Halftones"
> > by Blatner, etc.
>
> And...the description of dynamic range in that book completely agrees with
> my stated definition:
>
> "dynamic range describes the actual limits of how many tones the
> scanner can
> really differentiate from light to dark".

Roy, et al,

How come a property, such as dynamic range, as cited here, applies in this
"meaning"/"understanding" in digital imaging, and not in analog imaging?

Austin

At the risk of prolonging the interminable argument that has
developed around this topic, I offer an illustration of how Austin's
concepts might have "real world" relevance.

Some years ago, before I retired, I worked with a medical 
illustrator and was required to make photographic copies of her 
beautifully rendered 'carbondust' drawings. The differences in 
the gray tones in these black and white works were so subtle 
that I was having difficulty, within the normal workflow of our busy 
photo lab, in capturing them precisely. After many frustrating 
attempts, I was finally able to explain my problem to her in terms 
she could understand and to request her cooperation.

I produced a print of a stepwedge on normal contrast photo 
paper and taped it to the edge of her drawing board. I explained 
that it would make my life easier if she would constrain the tones 
in her drawings to ones on the strip. Using a tone that fell 
between the steps would be difficult for me to copy exactly. Not 
knowing a terminology for these concepts, I referred to the 
difference between the darkest and the lightest tones as 
"external contrast" and the difference between adjacent tones as 
"internal contrast." The proverbial 'lightbulb' went on over her 
head and she said henceforth she would follow my suggestion.

Cephalis

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:

> I do have A background in audio, but my "major" background is in 
imaging (as well as mobile robotics/Artificial Intelligence).

Austin, I sometimes think that most of my intelligence is artificial 
as well. ;-)

> > First,
> > "The Negative" by
> > Ansel Adams talks quite definitely about dynamic range.
> 
> Yes, and I believe, what was quoted at least, does agree with what 
>I have said.  You obviously interpret the same words differently ;-

I think that the definition of Dynamic Range applies as appropriately 
to audio, and electronics, as it does to photographic imaging.

Mike

Hi Austin,

I'm going to divide some of the responses to make them more readable.

> 
> Yeah, just like monitors are talked about in terms of "resolution", which
> means something completely different from the use of resolution to the rest
> of the world in every other application that uses that term.   Hum.

I do remember you having a beef with this before.  I declined to answer then
because I think its a moot point.  But, I think its an illustration of an overly
rigid application of technical concepts on your part.  The word "resolution" has
been a consistent "concept" for a long time.  Its basically the measure of discerning
information over the spacial dimension.  In the analog film and optics world, 
resolution is usually talked about in lines per mm or some equivalent.  When the
digital world came about, this wasn't the most convenient units so pixels
per inch seems to have taken over.  Same basic concept but very different units.
Now comes monitors.  Pretty much everybody associated with monitors wants
to refer to "how much stuff is on the screen".   From day one, the users, the
manufacturers, the buyers, the software, the hardware all cares most about 
how many pixels are there.  The term resolution has universally been used to
mean this is this context.  They could have all instead used pixels per inch to
spec monitors but they felt the unit "pixels per monitor" was much more useful
and informative.  

To me a consistent usage, in a clear cut context, with no
confusion, defines the term for that context. Arguing that people a wrong
when they are the ones in complete agreement is a misplaced effort.

> 
> > It doesn't matter how good the idea is,
> > I just can't imagine how it makes sense to use an existing term.  We have
> > to talk to other people, use other technologies, read specs, you name it.
> > Let's make it easy to communicate with the outside world!
> 
> Agreed, but that doesn't mean the term isn't being misused ;-)
> 
> Austin

Roy

Hi Roy,

> The word
> "resolution" has
> been a consistent "concept" for a long time.  Its basically the
> measure of discerning
> information over the spacial dimension.

Yes, I agree.

> They could have all instead used
> pixels per inch to
> spec monitors but they felt the unit "pixels per monitor" was
> much more useful
> and informative.

I have no problem with calling it "pixels", as it is pixels...but the point
is, it's not called pixels.  It's a misuse of the term "resolution" to say a
monitor has a resolution of 1280 x 1024, as no spatial dimension (well,
except "per monitor", which isn't really a very useful unit of measure,
since monitor sizes vary ;-) is "really" specified.  I think you understand
the point.

> To me a consistent usage, in a clear cut context, with no
> confusion, defines the term for that context. Arguing that people a wrong
> when they are the ones in complete agreement is a misplaced effort.

Well, for "us" pedestrians, which I am one of when it comes to monitors,
yes, it is a misplaced effort...but for someone who is "in the business",
it's a very important concept to understand.

Honestly, I don't consider the majority of people in "here" pedestrian when
it comes to imaging...as we are a "cut above" the "Joe point and shoot"
digital camera guys...and I do believe the correct use of the concept of
dynamic range won't be lost here.

Austin

on 4/5/02 11:37 AM, Austin Franklin wrote:

>>> Second, "Real World Scanning
>>> and Halftones"
>>> by Blatner, etc.
>> 
>> And...the description of dynamic range in that book completely agrees with
>> my stated definition:
>> 
>> "dynamic range describes the actual limits of how many tones the
>> scanner can
>> really differentiate from light to dark".
> 
> Roy, et al,
> 
> How come a property, such as dynamic range, as cited here, applies in this
> "meaning"/"understanding" in digital imaging, and not in analog imaging?

Because noise becomes much less of a limiting factor than chemical and
optical phenomena?

Todd

on 4/5/02 11:29 AM, Austin Franklin wrote:

>> The reason I'd stay with it even longer (Ya, I hear the
>> groans) is because underlying the contentious aspect of it is a search to
>> describe much of what we are looking for in a print; working towards or
>> against in our work; and a means to communicate about it.
> 
> Which is EXACTLY why I believe dynamic range is an important
> concept/property to understand and distinguish from density range.

I agree. I think they course this thread took has caused us to get lost in
the trees at points and loose sight of the woods. But that's nobody's fault,
it's challenging topic that needs to be hacked at from different angles.

Where I stand now is this: the concept of the ability to distinguish "micro
contrasts" within a larger "macro contrast" (density range) is interesting.
(Thanks for defining it as such Roy.) I think the formula you provided is
probably very workable in a scenario where noise is easily defined and it is
reasonably linear across the useable density range, so one or to points can
get integrated together, and give a useful number. However, when you get to
the point where you need to assess noise across the density range, because
it may be nonlinear within it, then I feel a different representation of
those measures would be more useful, like with a curve plot or histogram.

So, ultimately I like the concept you've maintained, it's just what it's
named and how it's applied/described that gives me pause. You've maintained
that for other fields the term dynamic range spoke to that concept, and it
should have in photography too, but instead the term got dumbed down to
represent density range. You're probably right. That may have occurred
because in an analog and non-linear world the calculations and descriptions
of that "contrast within a contrast" notion got more complicated, noise
becomes less of a limiting factor relative to optical phenomena, thus
formulas more complex than yours were applied, leaving the term "dynamic
range" unattended so to speak.

That's my little two minute summary of what I've taken from this thread so
far. What do you think?

Todd

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Hi Roy,
> 
> > The word
> > "resolution" has
> > been a consistent "concept" for a long time.  Its basically the
> > measure of discerning
> > information over the spacial dimension.
> 
> Yes, I agree.
> 
> > They could have all instead used
> > pixels per inch to
> > spec monitors but they felt the unit "pixels per monitor" was
> > much more useful
> > and informative.
> 
> I have no problem with calling it "pixels", as it is pixels...but the point
> is, it's not called pixels.  It's a misuse of the term "resolution" to say a
> monitor has a resolution of 1280 x 1024, as no spatial dimension (well,
> except "per monitor", which isn't really a very useful unit of measure,

I don't know what you mean by "useful", it seems to me to be about the
most important spec to tell you how must stuff you will be able to put on
the screen.  It's definitely the spec you need to pick a video card to run
it (I know these days most cards can handle more resolution than the
monitors but that hasn't always been the case).  

My main point is pragmatic and illustrative, we all know and agree what it
means, so let's get beyond any labeling of it as correct use or misuse.

> since monitor sizes vary ;-) is "really" specified.  I think you understand
> the point.
> 
> > To me a consistent usage, in a clear cut context, with no
> > confusion, defines the term for that context. Arguing that people a wrong
> > when they are the ones in complete agreement is a misplaced effort.
> 
> Well, for "us" pedestrians, which I am one of when it comes to monitors,
> yes, it is a misplaced effort...but for someone who is "in the business",
> it's a very important concept to understand.
> 
> Honestly, I don't consider the majority of people in "here" pedestrian when
> it comes to imaging...as we are a "cut above" the "Joe point and shoot"
> digital camera guys...and I do believe the correct use of the concept of
> dynamic range won't be lost here.
> 
> Austin

I've never used the term "pedestrian" in any way, manner, or form for
any people, ideas or anything in this group.

Roy

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Roy,
> 
> > So, how can we here is our niche, talk about coming up with a new idea,
> > new concept of what "dynamic range" means?
> 
> No one is coming up with any new concepts...  "We" are merely pointing out
> that the term has been "misapplied" in this "field", and that it attributes
> a different property than, though is loosely related to, density range.

Austin,

I think Todd's "lost in the trees at points and loose sight of the woods"
quote is right on.

> 
> > We a just a part of a large
> > community of imaging that long time ago has defined and has commonly used
> > this term to mean sometime very specific.
> 
> Can you show evidence of this?

I think the Ansel Adams book and the Real World Scanning references were
pretty relevant.  I'm glad to see you have read the scanning book.  You
quoted one sentence that contained "dynamic range describes the actual
limits of how many tones the scanner can really differentiate from light to
dark".  You seem to be associating:  dynamic range <--> how many tones,
when I think the real association is:  dynamic range <--> actual limits.
Reading just this one sentence might be a little ambiguous, but read the whole
paragraph.  Immediate following this sentence is the staircase example:
dynamic range <--> height of staircase,  bit depth <--> number of steps.
Later on he compares a scanner with "enormous dynamic range but only
256 steps" and a scanner with "lots of tiny steps and tiny dynamic range".
There's no way to interpret these two examples to mean dynamic range
is a measure of number of tones or steps!  
Do you wish to claim that this book and the three guys who wrote
it are wrong and misuse and misdefine the term??

If you look at the Adam's book there's a diagram that explicitly shows
"dynamic range".  He's talking about exposure and shows very clearly
dynamic range going from about Zone I to Zone IX saying its the "useful"
range of light values in the scene.  He even mentions how this dynamic
range of light values maps directly into the range of "useful" densities on
the negative.  Would you like to claim he's all wrong, too?

Please consider your position as it relates to these references.  These
are both very explicit references to dynamic range as it relates to imaging.

Regards,
Roy


> 
... monitor stuff snipped

> 
> Austin

Roy,

I'm sensing that some of us have locked horns when we are probably more in
agreement than out of agreement. Perhaps if we all surrender a little ground
we can turn this back into a useful discussion.

Is it possible that *some* people used the term dynamic range to describe
something one step more complex than density range? I think behind Austin's
absolutist rhetoric that is what he's saying.

Working with my sense of logic, which doesn't prove anything, let's look at
the bigger picture. Lets consider a common situation we as photographers
experience. Say through careful exposure and development we have a negative
with a beautiful delicate distribution of tones throughout it's useful
range. It would perfectly fit all it's tones on a given grade 2 paper. Let's
say that print's density range would be 2 units. If we could measure the
print on a pixel by pixel basis it would yield a perfect distribution of
tones in a histogram, right to the ends with no clipping. We could then
print that negative on a grade 3 paper, which may also yield a density range
of 2 units, but we "clip" tones from the image on both ends due to increased
contrast. It's histogram shows the clipping accordingly. We could even
extend the scenario to where we keep the print on grade 3 paper, but dodge
the shadows and burn the highlights, thus maintaining a higher internal
contrast through the midtones, without clipping the ends. It's density range
is still 2 units, and it's histogram looks more like the grade 2 print, at
least at the ends.

Something *is* different in each of these prints, but it is not the density
range. Is it possible that some people would say that the grade 2 print had
a greater dynamic range than the straight grade 3 print, and that the
manipulated grade 3 print might have had the greatest dynamic range of the
three? If not dynamic range, what would be that term?

Todd

> --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...>
> wrote:
>> Roy,
>> 
>>> So, how can we here is our niche, talk about coming up with a new idea,
>>> new concept of what "dynamic range" means?
>> 
>> No one is coming up with any new concepts...  "We" are merely pointing out
>> that the term has been "misapplied" in this "field", and that it attributes
>> a different property than, though is loosely related to, density range.
> 
> Austin,
> 
> I think Todd's "lost in the trees at points and loose sight of the woods"
> quote is right on.
> 
>> 
>>> We a just a part of a large
>>> community of imaging that long time ago has defined and has commonly used
>>> this term to mean sometime very specific.
>> 
>> Can you show evidence of this?
> 
> I think the Ansel Adams book and the Real World Scanning references were
> pretty relevant.  I'm glad to see you have read the scanning book.  You
> quoted one sentence that contained "dynamic range describes the actual
> limits of how many tones the scanner can really differentiate from light to
> dark".  You seem to be associating:  dynamic range <--> how many tones,
> when I think the real association is:  dynamic range <--> actual limits.
> Reading just this one sentence might be a little ambiguous, but read the whole
> paragraph.  Immediate following this sentence is the staircase example:
> dynamic range <--> height of staircase,  bit depth <--> number of steps.
> Later on he compares a scanner with "enormous dynamic range but only
> 256 steps" and a scanner with "lots of tiny steps and tiny dynamic range".
> There's no way to interpret these two examples to mean dynamic range
> is a measure of number of tones or steps!
> Do you wish to claim that this book and the three guys who wrote
> it are wrong and misuse and misdefine the term??
> 
> If you look at the Adam's book there's a diagram that explicitly shows
> "dynamic range".  He's talking about exposure and shows very clearly
> dynamic range going from about Zone I to Zone IX saying its the "useful"
> range of light values in the scene.  He even mentions how this dynamic
> range of light values maps directly into the range of "useful" densities on
> the negative.  Would you like to claim he's all wrong, too?
> 
> Please consider your position as it relates to these references.  These
> are both very explicit references to dynamic range as it relates to imaging.
> 
> Regards,
> Roy
> 
> 
>> 
> ... monitor stuff snipped
> 
>> 
>> Austin

Roy,

<snip>

> > I have no problem with calling it "pixels", as it is
> pixels...but the point
> > is, it's not called pixels.  It's a misuse of the term
> "resolution" to say a
> > monitor has a resolution of 1280 x 1024, as no spatial dimension (well,
> > except "per monitor", which isn't really a very useful unit of measure,
>
> I don't know what you mean by "useful", it seems to me to be about the
> most important spec to tell you how must stuff you will be able to put on
> the screen.

Sigh.  I said "useful UNIT OF MEASURE" not that the number wasn't "useful".
When comparing that number to ANOTHER monitor with the same resolution, it
give you NO information on how "big" the monitor is, you need "a"
measurement of monitor size.

> My main point is pragmatic and illustrative, we all know and agree what it
> means, so let's get beyond any labeling of it as correct use or misuse.

I know that, and I pointed that out when I first brought the misuse of the
term "resolution" into the conversation, but I take it you don't get why I
brought it up in the first place.

Austin

> > How come a property, such as dynamic range, as cited here,
> applies in this
> > "meaning"/"understanding" in digital imaging, and not in analog imaging?
>
> Because noise becomes much less of a limiting factor than chemical and
> optical phenomena?

I don't believe so.  Limiting or not doesn't mean it doesn't exist.  It may
make the significance of "it" less, no doubt.

Point is, it's really clear that WRT digital imaging, number of bits IS
dynamic range.  Many technical resources (not ones of Photoshop gurus) state
exactly that, as well as the Higgins book on Digital Signal Processing
clearly does.  Why are people willing to accept it "exists" as one "meaning"
when applied there, but as a different "meaning" when applied to chemical
prints.

Austin

--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:
> Roy,
> 
> I'm sensing that some of us have locked horns when we are probably more in
> agreement than out of agreement. Perhaps if we all surrender a little ground
> we can turn this back into a useful discussion.
> 
> Is it possible that *some* people used the term dynamic range to describe
> something one step more complex than density range? I think behind Austin's
> absolutist rhetoric that is what he's saying.

Hi Todd,

I believe that other than Austin being an instance of "*some* people", no-one
uses the term like Austin.  Obviously,  I've have not polled everyone in the world.
But I really think if Austin is claiming "there are others" he ought to be able
to cite a couple.  Correct me if I'm wrong but I'm asked for a reference many
times so far and they don't seem to be forth coming.  On the other hand I've
cited some fairly noteworthy people that agree with my interpretation.  I
really don't think its a "I SAY" versus "HE SAYS" issue.  I'm just the messenger.
I think it is a IMAGING WORLD SAYS versus AUSTIN SAYS issue  -- and since
that may not to obvious I'm trying to show that.

Just to reclarify a little:  Dynamic range is the range of useful light values or
their representation in an Image.  Range is defined by a Maximum and a Minimum.
Describing  the range is the max and min, the size of the range would be the difference.
By "useful" (I liked Ansel's use of this word) I mean there may be light values
too dark or too bright to discern any information.  In photo language high values
that are blocked up or shadows that have no detail are NOT useful and
would not be included in the Dynamic Range.  Finally I say "light values" or
"their representation", what I mean is:  Imaging goes thru lots of steps, we
start out with actual light waves from a scene.  The range of useful light
intensities i.e. what you measure with your spot meter is the dynamic range
of the scene.  Here the dynamic range would be stops or EV (exposure values).
Once we put the image on film, the film itself doesn't have "light", it 
represents the information as densities.  Now the dynamic range is the
useful density range of the film.  Down in the film-base+fog doesn't count nor
does the blown out highlights (dense  part of negative).  Here we could
actually talk about the dynamic range of the type of film i.e. DyR of Tmax
for instance or we could talk about the DyR of a specific image on film.
When you get to the scanner, you've its DyR has be at least as large and
its min thru max has to completely cover the DyR of the image on film.
Again here DyR of the scanner is measured in density and its also
important to qualify with "useful" density range -- i.e. it has to discern
information within that Dynamic Range.   Most specs only quote the max
density because its assumed that everything from 0 to max is "useful".
So its a little more complex than just density range, but it never has the
flavor of "number of tones".   The staircase model seems so perfect
I'd like to keep pointing back to it.

> 
> Working with my sense of logic, which doesn't prove anything, let's look at
> the bigger picture. Lets consider a common situation we as photographers
> experience. Say through careful exposure and development we have a negative
> with a beautiful delicate distribution of tones throughout it's useful

This is a nice example, I'll throw some comments in as we go.

> range. It would perfectly fit all it's tones on a given grade 2 paper. Let's
> say that print's density range would be 2 units. If we could measure the
> print on a pixel by pixel basis it would yield a perfect distribution of
> tones in a histogram, right to the ends with no clipping. We could then
> print that negative on a grade 3 paper, which may also yield a density range
> of 2 units, but we "clip" tones from the image on both ends due to increased
> contrast. It's histogram shows the clipping accordingly. We could even
> extend the scenario to where we keep the print on grade 3 paper, but dodge
> the shadows and burn the highlights, thus maintaining a higher internal
> contrast through the midtones, without clipping the ends. It's density range
> is still 2 units, and it's histogram looks more like the grade 2 print, at
> least at the ends.

Great, the paper itself has a density range of 2 in each case.  Notice
however that how that range maps into the original scene is different.
Think about the dynamic range of the original scene that is now captured
on the two different prints.  In the grade 2 case, every tone in the original
scene (i.e. every tone in the original dynamic range) is represented in the
dynamic range of the final print.  Now in the grade 3 case, a section of the
darkest tones in the original all map into black on the print. Likewise a
section of the lightest tones all map into white.  So only part of the original
dynamic range of the scene shows up in the dynamic range of the picture.
Seeing how human beings are, they are more interested in images than
paper.  So when they say one print has more dynamic range they are really
thinking about how much of the dynamic range of the original image they
are seeing in the final print.

Makes me also wonder about doing a grade 1 print.  Here the DyR of 
original scene would be the same as in the grade 2.  But we wouldn't be
using the whole DyR of the paper, (no pure whites and no pure blacks)
and our "perception" would pick that up as the deficiency.  Interesting
how our brain would notice a deficiency either way.

> 
> Something *is* different in each of these prints, but it is not the density
> range. Is it possible that some people would say that the grade 2 print had
> a greater dynamic range than the straight grade 3 print, and that the
> manipulated grade 3 print might have had the greatest dynamic range of the

We're certainly getting in a nebulous area here.  Maybe what we are effectively
simulating more dynamic range in the original than was really there.  
Remember we are always manipulating the brain to produce a perception.
I guess the local contrast would be higher and the perception of
sharpness would also be enhanced.  Kind of like "unsharp masking" using the
real film method not the photoshop filter.

> three? If not dynamic range, what would be that term?
> 
> Todd
> 

Roy

--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:

> Roy,
> 
> I'm sensing that some of us have locked horns when we are probably more in
> agreement than out of agreement. Perhaps if we all surrender a little ground
> we can turn this back into a useful discussion.
> 
> Is it possible that *some* people used the term dynamic range to describe
> something one step more complex than density range? I think behind Austin's
> absolutist rhetoric that is what he's saying.
> 
> Working with my sense of logic, which doesn't prove anything, let's look at
> the bigger picture. Lets consider a common situation we as photographers
> experience. Say through careful exposure and development we have a negative
> with a beautiful delicate distribution of tones throughout it's useful
> range. It would perfectly fit all it's tones on a given grade 2 paper. Let's
> say that print's density range would be 2 units. If we could measure the
> print on a pixel by pixel basis it would yield a perfect distribution of
> tones in a histogram, right to the ends with no clipping. We could then
> print that negative on a grade 3 paper, which may also yield a density range
> of 2 units, but we "clip" tones from the image on both ends due to increased
> contrast. It's histogram shows the clipping accordingly. We could even
> extend the scenario to where we keep the print on grade 3 paper, but dodge
> the shadows and burn the highlights, thus maintaining a higher internal
> contrast through the midtones, without clipping the ends. It's density range
> is still 2 units, and it's histogram looks more like the grade 2 print, at
> least at the ends.
> 
> Something *is* different in each of these prints, but it is not the density
> range. Is it possible that some people would say that the grade 2 print had
> a greater dynamic range than the straight grade 3 print, and that the
> manipulated grade 3 print might have had the greatest dynamic range of the
> three? If not dynamic range, what would be that term?
> 
> Todd
> 
> 
> 
> 
> 
> > --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...>
> > wrote:
> >> Roy,
> >> 
> >>> So, how can we here is our niche, talk about coming up with a new idea,
> >>> new concept of what "dynamic range" means?
> >> 
> >> No one is coming up with any new concepts...  "We" are merely pointing out
> >> that the term has been "misapplied" in this "field", and that it attributes
> >> a different property than, though is loosely related to, density range.
> > 
> > Austin,
> > 
> > I think Todd's "lost in the trees at points and loose sight of the woods"
> > quote is right on.
> > 
> >> 
> >>> We a just a part of a large
> >>> community of imaging that long time ago has defined and has commonly used
> >>> this term to mean sometime very specific.
> >> 
> >> Can you show evidence of this?
> > 
> > I think the Ansel Adams book and the Real World Scanning references were
> > pretty relevant.  I'm glad to see you have read the scanning book.  You
> > quoted one sentence that contained "dynamic range describes the actual
> > limits of how many tones the scanner can really differentiate from light to
> > dark".  You seem to be associating:  dynamic range <--> how many tones,
> > when I think the real association is:  dynamic range <--> actual limits.
> > Reading just this one sentence might be a little ambiguous, but read the whole
> > paragraph.  Immediate following this sentence is the staircase example:
> > dynamic range <--> height of staircase,  bit depth <--> number of steps.
> > Later on he compares a scanner with "enormous dynamic range but only
> > 256 steps" and a scanner with "lots of tiny steps and tiny dynamic range".
> > There's no way to interpret these two examples to mean dynamic range
> > is a measure of number of tones or steps!
> > Do you wish to claim that this book and the three guys who wrote
> > it are wrong and misuse and misdefine the term??
> > http://www.badgergraphic.com/
> > If you look at the Adam's book there's a diagram that explicitly shows
> > "dynamic range".  He's talking about exposure and shows very clearly
> > dynamic range going from about Zone I to Zone IX saying its the "useful"
> > range of light values in the scene.  He even mentions how this dynamic
> > range of light values maps directly into the range of "useful" densities on
> > the negative.  Would you like to claim he's all wrong, too?
> > 
> > Please consider your position as it relates to these references.  These
> > are both very explicit references to dynamic range as it relates to imaging.
> > 
> > Regards,
> > Roy
> > 
> > 
> >> 
> > ... monitor stuff snipped
> > 
> >> 
> >> Austin

Hi Roy,

<snip>

> You
> quoted one sentence that contained "dynamic range describes the actual
> limits of how many tones the scanner can really differentiate
> from light to
> dark".  You seem to be associating:  dynamic range <--> how many tones,
> when I think the real association is:  dynamic range <--> actual limits.

READ IT.  "actual limits of HOW MANY tones".

It is unquestionable that the number of bits IS the LIMIT of the dynamic
range of a digital system.  Even the Higgins book CLEARLY says that, and I
quote:

"The relationship between number of bits, M, recorded digitally and the
dynamic range DR in dB is

DR(dB) = 20log10(2**M)"

and it qualifies the 20 at the bottom saying it is typically 10log10...

> Reading just this one sentence might be a little ambiguous,

That statement is perfectly clear in and of it self...and he should have
left it at that, but unfortunately...

> but
> read the whole
> paragraph.  Immediate following this sentence is the staircase example:
> dynamic range <--> height of staircase,  bit depth <--> number of steps.

He states he is paraphrasing from Bruce Frasier, who is a PhotoShop guru,
not a hardware engineer (or a signal processing expert).  Look, this is just
not debatable.  Number of bits IS dynamic range.  I thought you said you
were an engineer?  I take it not an electrical or computer engineer.  That
is just so "basic" to anyone who has any experience in digital signal
processing.

Again, supporting exactly what I've said, the term dynamic range is very
misunderstood, and is very misapplied by people who don't have the
background to understand that they are misapplying it...as no one ever
really explained it to them, and the proliferation of misinformation on it
that is out there.

Go read this:

http://www.prosig.com/signal-processing/adcbits.html

BTW, none of the authors of the book "Real World..." have ever designed any
scanners, much less any digital imaging systems.  The main author is an
expert on QuarkExpress and Photoshop.  He is NOT an electrical engineer, and
I am reasonably sure, doesn't completely understand what he is writing about
with respect to dynamic range.  He certainly understands scanning enough to
write a decent book on scanning, but that doesn't mean he gets every
technical detail "right".

> Please consider your position as it relates to these references.  These
> are both very explicit references to dynamic range as it relates
> to imaging.

I have "considered" my position and I am unquestionably right, not only in
what I've said before, but unquestionably so in this case.  This FACT that
dynamic range is limited by bit depth is so basic to the discussion of
digital signal processing, which is what we are talking about when we talk
about bits and dynamic range.

Here are some additional references of OTHER professionals who explain that
dynamic range of a digital system is the same thing as bit depth:

http://www.styrex.se/kunskapsbanken/STYREX_HTML/Tutorial/realtime.html

Where the go on to simply say "The digitisers vary in conversion speed,
dynamic range (number of bits in the result), stability and linearity."

http://www.ndt.net/article/0598/linas_eq/linas_eq.htm

Go down half way, and there is a table that shows number of bits required
for a different dynamic ranges...and it conforms to the equation I listed
out of Higgins above.

And a very interesting application of dynamic range:

http://www2.erdas.com/supportsite/Glossary.htm

"radiometric resolution - the dynamic range, or number of possible data file
values, in each band. This is referred to by the number of bits into which
the recorded energy is divided. See pixel depth."

And from a manual for some medical imaging software, but relating dynamic
range to monitors (as they apparently do understand digital imaging, since
that is what they do ;-), showing they believe number of bits represents
dynamic range, as well as dynamic range is number of tones:

http://www.expasy.ch/UIN/html1/projects/osiris/osirismanual.html

"Image dynamic range versus displayed dynamic range
The dynamic range of some images may often exceed the dynamic range of
intensity levels that can be displayed at one time on a screen. The software
performs an optimal mapping of the image intensity values into the display
range. Typically medical images have an intrinsic dynamic depth range of up
to 12 or 16 bits while most of the common display systems support 8 bit
displays that allow only 256 levels to be displayed simultaneously on the
screen. Interactive adjustment is made in real time on the available dynamic
range of the display (typically 256 gray levels) and when done, the image in
its full dynamic range is remapped on the screen."

And...a discussion on digital signal processing:

http://www.qsl.net/on7yd/136narro.htm

"The number of bits of the A-D convertor determines the dynamic range of the
spectrum."

And since I'm getting tired, and this is time consuming, here is a final
resource (requires registration):

http://www.the-scientist.com/yr1999/august/profile2_990830.html

"The dynamic range of a pixel (vertical resolution) is a function of the
linear well size and noise. A pixel that can hold 500,000 electrons with a
read noise of five electrons will offer a signal-to-noise ratio of 100,000:1
or approximately 17 bits of information (dynamic range = 2n, where n = the
number of bits). To take full advantage of this, the on-board processor of
the chip and the downstream components need to have 16- to 18-bit
capability."

Austin

Roy,

> > Is it possible that *some* people used the term dynamic range
> to describe
> > something one step more complex than density range? I think
> behind Austin's
> > absolutist rhetoric that is what he's saying.
>
> Hi Todd,
>
> I believe that other than Austin being an instance of "*some*
> people", no-one
> uses the term like Austin.

You say that, but it isn't true.  In audio, dynamic range IS clearly more
than just the range of the highest voltage to the lowest voltage, Higgins
clearly shows that.  Dynamic range IS more complex than density range for
imaging, and the equation for dynamic range and density range clearly show
that.

> But I really think if Austin is claiming "there are others" he
> ought to be able
> to cite a couple.

I have, but you interpret their words as meaning something else.  Even
Higgins states what I say...but you claim that because he uses the word
"audio", even though it is clearly listed as an "EXAMPLE", and happens to
use audio, that what he says is only applicable to audio.  That's a
misinterpretation.

> Correct me if I'm wrong but I'm asked for a
> reference many
> times so far and they don't seem to be forth coming.

Again, you say that, but it's not true.  I've given references.  You just
claim that they aren't applicable, or claim that they mean something
different than I say they do.  Sigh.

> On the
> other hand I've
> cited some fairly noteworthy people that agree with my interpretation.

Noteworthy in something, but not noteworthy in engineering or signal
processing.

> I
> really don't think its a "I SAY" versus "HE SAYS" issue.  I'm
> just the messenger.

That's my line...I didn't make up the dynamic range equation, it IS what it
IS, and it clearly, by the actual equation, is not the same as density
range.

> I think it is a IMAGING WORLD SAYS versus AUSTIN SAYS issue  -- and since
> that may not to obvious I'm trying to show that.

Well, as I've said, your references are not engineers or really in-depth
technical people, they are primarily Photoshop gurus.  From what I can tell,
none of them have ever designed any imaging equipment.  How would they know
what dynamic range really is, or that what they are told is right or wrong,
or what is the significance of what they are told?

> Just to reclarify a little:  Dynamic range is the range of useful
> light values or
> their representation in an Image.  Range is defined by a Maximum
> and a Minimum.
> Describing  the range is the max and min, the size of the range
> would be the difference.

Yes, range is defined by max and min, and since the range you are defining
IS a range of density, all max and min gives you is the DENSITY RANGE.  It
does not give you the dynamic range, as clearly shown by the dynamic range
equation.

> By "useful" (I liked Ansel's use of this word) I mean there may
> be light values
> too dark or too bright to discern any information.

That's called thresholding.

> In photo
> language high values
> that are blocked up or shadows that have no detail are NOT useful and
> would not be included in the Dynamic Range.

They would not be included in the DENSITY range.  Since they are outside the
density range, of course they have no dynamic range.

> When you get to the scanner, you've its DyR has be at least as large and
> its min thru max has to completely cover the DyR of the image on film.

Not right, it's DENSITY range that has to cover the DENSITY range of the
film.

dMax and dMin in the real world scene are simply represented on film by
"some" dMax and dMin of the film, that is not at all calibrated to the real
world.  Same with scanning and then printing.  You can scan film that has
one dMin and dMax, and then print it, but the values you get out are nothing
but relative value to each other, they in no way bear any resemblance to the
actual measurable dMax, dMin values that are on the film.

You can print a negative with a density range of 1 and another negative with
a density range of 2, but get a print density range of 2 for both negatives.

> Again here DyR of the scanner is measured in density

Dynamic range is never measured in density, it is measured in dB.  There is
a reason for that, simply because dB shows how much is there, as opposed to
density range which doesn't say a wit about what's in between.  Dynamic
range is a property of the "discernability" of density.

> The staircase model seems so perfect
> I'd like to keep pointing back to it.

Yeah, but your belief of what it represents is mistaken.  The bottom step is
dMin, the top step is dMax and the number of steps is the dynamic range (and
in the digital world, also the bit depth).  This probably got misinterpreted
because someone, sometime, used a staircase example to try to describe
dynamic range to someone else, who didn't quite understand it...etc.  Kind
of like telephone.

Obviously you want to believe what you want to believe, and/or just don't
want to understand what dynamic range really means.  I know you believe you
understand it, but from what you cite, you don't.  You use references that
don't understand it themselves, and when I cite references that are quite
technical, you either ignore them, or misinterpret them.  I know you can say
that I am misinterpreting them...but I HAVE designed imaging equipment, and
audio equipment, and subjected my self to PROFESSIONAL peer review.

You are obviously an excellent photographer, as I've visited your web site,
and find your work to be outstanding.  Perhaps it might be useful if you
stated what your background is that is applicable to this discussion.  You
said you have "a couple of degrees in EE", but haven't said at all what your
"field" is (or was), or if you've actually done any applicable design work,
or used the concept of dynamic range in any of your work.

You've never answered what is "dynamic" about YOUR belief in what dynamic
range means.  I believe, there is nothing dynamic about what you believe
dynamic range is, and I believe dynamic makes perfect sense when applied to
what I say "dynamic range" is.

Austin

on 4/5/02 7:19 PM, Austin Franklin wrote:

>>> How come a property, such as dynamic range, as cited here, applies in this
>>> "meaning"/"understanding" in digital imaging, and not in analog imaging?
>>> 
>> Because noise becomes much less of a limiting factor than chemical and
>> optical 
>> phenomena?
>> 
> I don't believe so.  Limiting or not doesn't mean it doesn't exist.  It may
> make the significance of "it" less, no doubt.

So just when are you going to define "noise" WRT to a silver print and an
inkjet print so that we have a basis to judge whether it's existence is
RELEVANT? You've been asked to do so numerous times but instead of answering
you repeat that "just because you can't see it doesn't mean it doesn't
exist". I'm not interested in it's spiritual and metaphysical existence, I
think it is relevant whether or not the noise is large enough to be limiting
to perception. Please stop skirting that issue.

> Point is, it's really clear that WRT digital imaging, number of bits IS
> dynamic range.  Many technical resources (not ones of Photoshop gurus) state
> exactly that, as well as the Higgins book on Digital Signal Processing
> clearly does.  Why are people willing to accept it "exists" as one "meaning"
> when applied there, but as a different "meaning" when applied to chemical
> prints.

Because it's the difference between analog and digital, continuous tone or
steps. Let me phrase it with a question: what is the analog equivalent of a
bit? And don't tell me contrast, because a bit is on vs off, contrast has
VIRTUALLY (emphasized to indicate I'm not being absolutist, I don't want to
get bogged down in the quantum physics of this again) infinite positions
between.

Todd

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, April 05, 2002 8:37 AM
Subject: RE: [Digital BW] Thoughts about Imaging


> > > Second, "Real World Scanning
> > > and Halftones"
> > > by Blatner, etc.
> >
> > And...the description of dynamic range in that book completely agrees
with
> > my stated definition:
> >
> > "dynamic range describes the actual limits of how many tones the
> > scanner can
> > really differentiate from light to dark".
>
> Roy, et al,
>
> How come a property, such as dynamic range, as cited here, applies in this
> "meaning"/"understanding" in digital imaging, and not in analog imaging?
>
Austin,

I have never thought of it as a "property" but as a sometimes useful
mathematical relationship that compares and contrasts actual physical
properties. Perhaps this is part of our misunderstanding.

Martin

> So just when are you going to define "noise" WRT to a silver print and an
> inkjet print so that we have a basis to judge whether it's existence is
> RELEVANT?

We have shown how to do it with inkjet prints with pretty reasonable
certainty, and shown some proposed methodologies for doing so with chemical
prints.

> Please stop skirting that issue.

Well, I haven't!  Both Johnny Brownlow and I HAVE spoken to this issue.

> Let me phrase it with a question: what is the analog
> equivalent of a
> bit?

It depends on what you are representing with that "bit" (voltage,
current...), what the range of values can be, and what the noise is in that
"system" (determines how many bits are needed for the A/D).

Since we're talking about scanners, sort of, I'll relate it to that.  For a
typical A/D, which has a voltage swing of +- 3V, that makes it have an
absolute range of 6V.  If the measurable noise in the system was, say, .01V,
then you would have a dynamic range of 6V/.01V or 600, and you would use an
A/D converter that would accommodate that "range"...which would be one that
has enough bits to cover 1024 (next binary step up from 600), and that would
take 10 bits.  So, 6V / 1024 means each bit represents a voltage change of
~0.005.  The bottom bit would be pretty much "in the noise", but that doesn'
t effect the overall voltage is represented by a particular binary
number...as it'll be accurate to the noise, or +-.005V (1/2 the noise will
be high, and 1/2 low).

In the case I gave, the analog equivalent of one bit is ~0.005 +- 0.005V ;-)

Austin

On 4/6/02 darkroom@... wrote:

>> So just when are you going to define "noise" WRT to a silver print and an
>> inkjet print so that we have a basis to judge whether it's existence is
>> RELEVANT?
>
>We have shown how to do it with inkjet prints with pretty reasonable
>certainty, and shown some proposed methodologies for doing so with chemical
>prints.

I would have to think about chemical prints but yes I think that has been
addressed convincingly. The noise floor is the variation in the paper
base and the minimum discernible signal has also been defined.

-- 
John Brownlow

http://www.pinkheadedbug.com

Todd,

I just want to point out that dynamic range in photography is generally
discussed along with contrast. You don't need to get everything into a
single value.

Austin is discussing an interesting relationship but it is not the
relationship commonly called dynamic range in photography, i.e. the ratio of
lightest and darkest which is frequently quantified as the density range. I
believe that the property he is discussing is of interest but I don't see it
as a new or expanded definition of this ratio.

What you mention below seems to be simply an issue of contrast. The response
to exposure may become steeper or shallower depending upon the grade of the
paper but once the print is a done deal the original grade is no longer a
contributing factor. You are right and contrast is independent of density
range and of what is commonly called dynamic range.

Phil Davis discussed this at great length in "Beyond the Zone System" with
lots of curves showing how Scene Brightness Range maps to the negative by
way of the film's exposure response curve and how the negatives density
range maps to the print by way of the paper's exposure response curve.

It is interesting that he manages to get through 200+ pages of photographic
sensitometry and never even uses the term dynamic range.

I have to agree with Roy that it serves little purpose to redefine dynamic
range as something different than how it is commonly used in photography. I
think that we would be better served at this point if there was a different
term for the relationship Austin is describing. I know Austin will not like
this but if the term dynamic range has already been appropriated, rightly or
wrongly, trying to switch just adds to the confusion.

Martin

P.S. Since when do prints have pixels? <G>

----- Original Message -----
From: "Todd Flashner" <tflash@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, April 05, 2002 3:16 PM
Subject: Re: [Digital BW] Thoughts about Imaging


> Roy,
>
> I'm sensing that some of us have locked horns when we are probably more in
> agreement than out of agreement. Perhaps if we all surrender a little
ground
> we can turn this back into a useful discussion.
>
> Is it possible that *some* people used the term dynamic range to describe
> something one step more complex than density range? I think behind
Austin's
> absolutist rhetoric that is what he's saying.
>
> Working with my sense of logic, which doesn't prove anything, let's look
at
> the bigger picture. Lets consider a common situation we as photographers
> experience. Say through careful exposure and development we have a
negative
> with a beautiful delicate distribution of tones throughout it's useful
> range. It would perfectly fit all it's tones on a given grade 2 paper.
Let's
> say that print's density range would be 2 units. If we could measure the
> print on a pixel by pixel basis it would yield a perfect distribution of
> tones in a histogram, right to the ends with no clipping. We could then
> print that negative on a grade 3 paper, which may also yield a density
range
> of 2 units, but we "clip" tones from the image on both ends due to
increased
> contrast. It's histogram shows the clipping accordingly. We could even
> extend the scenario to where we keep the print on grade 3 paper, but dodge
> the shadows and burn the highlights, thus maintaining a higher internal
> contrast through the midtones, without clipping the ends. It's density
range
> is still 2 units, and it's histogram looks more like the grade 2 print, at
> least at the ends.
>
> Something *is* different in each of these prints, but it is not the
density
> range. Is it possible that some people would say that the grade 2 print
had
> a greater dynamic range than the straight grade 3 print, and that the
> manipulated grade 3 print might have had the greatest dynamic range of the
> three? If not dynamic range, what would be that term?
>
> Todd
>
>
>
>
>
> > --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin"
<darkroom@i...>
> > wrote:
> >> Roy,
> >>
> >>> So, how can we here is our niche, talk about coming up with a new
idea,
> >>> new concept of what "dynamic range" means?
> >>
> >> No one is coming up with any new concepts...  "We" are merely pointing
out
> >> that the term has been "misapplied" in this "field", and that it
attributes
> >> a different property than, though is loosely related to, density range.
> >
> > Austin,
> >
> > I think Todd's "lost in the trees at points and loose sight of the
woods"
> > quote is right on.
> >
> >>
> >>> We a just a part of a large
> >>> community of imaging that long time ago has defined and has commonly
used
> >>> this term to mean sometime very specific.
> >>
> >> Can you show evidence of this?
> >
> > I think the Ansel Adams book and the Real World Scanning references were
> > pretty relevant.  I'm glad to see you have read the scanning book.  You
> > quoted one sentence that contained "dynamic range describes the actual
> > limits of how many tones the scanner can really differentiate from light
to
> > dark".  You seem to be associating:  dynamic range <--> how many tones,
> > when I think the real association is:  dynamic range <--> actual limits.
> > Reading just this one sentence might be a little ambiguous, but read the
whole
> > paragraph.  Immediate following this sentence is the staircase example:
> > dynamic range <--> height of staircase,  bit depth <--> number of steps.
> > Later on he compares a scanner with "enormous dynamic range but only
> > 256 steps" and a scanner with "lots of tiny steps and tiny dynamic
range".
> > There's no way to interpret these two examples to mean dynamic range
> > is a measure of number of tones or steps!
> > Do you wish to claim that this book and the three guys who wrote
> > it are wrong and misuse and misdefine the term??
> >
> > If you look at the Adam's book there's a diagram that explicitly shows
> > "dynamic range".  He's talking about exposure and shows very clearly
> > dynamic range going from about Zone I to Zone IX saying its the "useful"
> > range of light values in the scene.  He even mentions how this dynamic
> > range of light values maps directly into the range of "useful" densities
on
> > the negative.  Would you like to claim he's all wrong, too?
> >
> > Please consider your position as it relates to these references.  These
> > are both very explicit references to dynamic range as it relates to
imaging.
> >
> > Regards,
> > Roy
> >
> >
> >>
> > ... monitor stuff snipped
> >
> >>
> >> Austin
>
>
>
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<snip>
> Dynamic range is never measured in density, it is measured in dB.  There is
> a reason for that, simply because dB shows how much is there, as opposed to
> density range which doesn't say a wit about what's in between.  Dynamic
> range is a property of the "discernability" of density.

Austin,

I'm snipping from two separate posts to conserve space.

This is the linearity issue which I'm having trouble to get a handle on.
Doesn't DyR expressly assume that the component (scanner, monitor, paper)
has the capacity to delineate all tones within it's range pretty much
equally (linearly)? For instance it is assumed a scanner is able to discern
tones of similar difference equally across it's density range? (I would
assume that is what the pre-calibration is for, to linearize the A/Ds
conversion to the spectral output of the bulb.) With that assumption when
you say "dB shows how much is there, as opposed to density range which
doesn't say a wit about what's in between." it means that you can assume
that all of what's in between is represented equally, or at least capable of
being represented equally.

What I'm getting at is what does your DyR formula tell us about a print on
litho paper, which has a great range, but few tones between? (For the
purpose of this discussion lets not look at litho as being only pure black
as pure what, lets assume it has at least 2 dark shades and 2 light shades,
but no midtones.) It's not "noise" that is diluting it's intermediary tones.
So how will your formula describe, or account for that characteristic?

Furthermore, in the case of a scanner, "noise" only needs to be considered
in the dense regions of the film, right? Why is that? Would it be because
that is the only area in which it is of a significant value? If "noise" (I
have to keep it in quotes until it's defined (sigh ;-))) were as irrelevant
in the dense regions of film as in the thin regions, could it not similarly
be considered irrelevant, and thus dropped? Couldn't that be the case with
photo paper, noise is dropped leaving DyR as dMax - dMin?

<Snip>

Todd wrote:
>> So just when are you going to define "noise" WRT to a silver print and an
>> inkjet print so that we have a basis to judge whether it's existence is
>> RELEVANT?

Austin wrote:
> We have shown how to do it with inkjet prints with pretty reasonable
> certainty, and shown some proposed methodologies for doing so with chemical
> prints.

My apologies. Please restate it (copy and paste is fine) because all I
remember you saying is that you would take a few samples of a single tone
that lies within the range. I don't recall you giving the noise you are
measuring a name. You may have done so, but I lost it.
 
>> Please stop skirting that issue.
> 
> Well, I haven't!  Both Johnny Brownlow and I HAVE spoken to this issue.

Please see above and bottom.
 
>> Let me phrase it with a question: what is the analog
>> equivalent of a
>> bit?
> 
> It depends on what you are representing with that "bit" (voltage,
> current...), what the range of values can be, and what the noise is in that
> "system" (determines how many bits are needed for the A/D).

If you would be so kind, I'd *really* like to keep the discussion focused on
conventional photo materials for a while. See below.

At this point I think it would be extremely helpful if you could summarize
what you are still contending, or not, about what dynamic range as it
relates to conventional photography. Sometimes it's a tone count, others
times not. Sometimes it's expressed as db, others not. And you've still yet
to define noise (that I can remember, only that you would sample "it"),
which is the part of your equation that distinguished DyR from dMax - dMin.
That is simply too critical a concept to skimp on.

You must admit, the bent of your argument is really based upon an
electronic/digital orientation, and you really don't address the questions
that relate to analog-output/contone/conventional-photography with equal
vigor - which is the only place you've encountered disagreement from anyone.
So it's really hard to gauge where you stand on those issues.

Sorry, but I just think it's helpful if we each regroup from time to time so
we are clear on what the other person is still holding as a conviction and
what they've dropped. I did it myself earlier in the day and asked for your
response but none came. I'd hate for some of us to be in agreement and not
know it. ;-)

Thanks,
Todd

Hi Austin,

Well at least you did come thru with references.  Thank you. I've
read thru them all at least to find what was relevant.  There is a lot
of information.  My biggest disappointment though is that they are all
audio digital signal processing articles with maybe the exception of the
Osiris Manual.  I'm really not prepared nor do I think its appropriate to
argue this whole thing on an audio level.

I spent time on your original Higgin's book, looked at the formula, the diagram
and the derivation for audio.  I thought about interpreting the info for
imaging (particularly from the point of view: what we perceive) and came up 
with a way to use the formula for images.  I also looked at the way
you interpreted it.  Right or wrong I think we both have interpretations
that are at least mathematically reasonable.  From my point of
view, your way made less intuitive sense than mine, but I perserved and
tried to understand what the end result meant.  I.e.  could I conceptualize
the quality or property so defined.  Mine is certainly pretty simple (in fact
I think you believe its too simple).  But I've yet to really come up with a
feeling for yet except for maybe number of tones.  It seems several others
on the list are also trying to conceptualize it, too.

Anyway, given all that, I looked at a lot of the imaging literature and the
descriptions of dynamic range all seem to agree with my view.  Some may
be somewhat ambiguous but I've not seen anything clearly contradictory.
Scanner hardware specs all use the same terminology.  
I described in fair detail how to view DyR as an image passed thru various
stages, so I made a practical argument as well.  

So here we are.  You've pretty much blown off all the "experts" in imaging
saying they are not engineers and don't understand -- only audio experts
know what this is all about.

> 
> Dynamic range is never measured in density, it is measured in dB.

Minor question: If dynamic range is a measure of how many gray tones 
there are, how come its in dB and not just an integer.   Why doesn't
it just say there are 237 grays in this image??

Somehow, I'm never going to feel good about my image having 63dB
of dynamic range.  Maybe I can up it to 71dB and beat the other guy :)

  There is
> a reason for that, simply because dB shows how much is there, as opposed to
> density range which doesn't say a wit about what's in between.  Dynamic
> range is a property of the "discernability" of density.
> 
> > The staircase model seems so perfect
> > I'd like to keep pointing back to it.
> 
> Yeah, but your belief of what it represents is mistaken.  The bottom step is
> dMin, the top step is dMax and the number of steps is the dynamic range (and
> in the digital world, also the bit depth).  This probably got misinterpreted
> because someone, sometime, used a staircase example to try to describe
> dynamic range to someone else, who didn't quite understand it...etc.  Kind
> of like telephone.
> 
> Obviously you want to believe what you want to believe, and/or just don't
> want to understand what dynamic range really means.  I know you believe you
> understand it, but from what you cite, you don't.  You use references that
> don't understand it themselves, and when I cite references that are quite

Well, terminology aside.  Adams certainly had enough understanding of his
photography for me.  And the scanning book sure is more informative on
the ins and outs of scanning.

> technical, you either ignore them, or misinterpret them.  I know you can say
> that I am misinterpreting them...but I HAVE designed imaging equipment, and
> audio equipment, and subjected my self to PROFESSIONAL peer review.
> 
> You are obviously an excellent photographer, as I've visited your web site,
> and find your work to be outstanding.  Perhaps it might be useful if you
> stated what your background is that is applicable to this discussion.  You
> said you have "a couple of degrees in EE", but haven't said at all what your
> "field" is (or was), or if you've actually done any applicable design work,
> or used the concept of dynamic range in any of your work.

Not that it matters much, but BSEE MIT, MSEE Stanford, My field has been
mostly computer science.  Personally designed and personally written a ton of code.
I was the head technical person starting a company with 4 people and 
growing it to several thousand.  Not much in peer reviews, all the techie
people worked for me, sorry :).  Seriously, I worked in every aspect of computers
and what was connected to them.  Figuring out how systems worked and how
to make them work for you in lots of different fields is what I've always done.

You can probably claim more dynamic range usage in your specific area, 
but my diversity has served me well. 

> 
> You've never answered what is "dynamic" about YOUR belief in what dynamic
> range means.  I believe, there is nothing dynamic about what you believe
> dynamic range is, and I believe dynamic makes perfect sense when applied to
> what I say "dynamic range" is.

So you're asking how I think the English definition of "dynamic" is relevant to
the technical definition??  I thought we were talking about a technical
definition that was explicit and precise technically.  No?

Actually, the word I've equated "dynamic" to is "useful".  In ranges such as
exposure, Zones, density.  The useful part of those ranges is where the
image information is.  The part of the range is "dynamic", the parts outside
are dead, useless, have no image.  Hence "dynamic" rather than "dead".
Its just an English language analogy, but then that's all you asked for.

> 
> Austin

I guess we're pretty much at an impasse.  Too bad.  I think I found some
pretty useful ways to view the term "dynamic range" as images passed
thru various steps and what it meant.

Sorry about any grumpy tone to this. I'm frustrated as I'm sure you are.
I gotta go make some pictures.

Roy

on 4/6/02 12:25 AM, John Brownlow wrote:

>>> So just when are you going to define "noise" WRT to a silver print and an
>>> inkjet print so that we have a basis to judge whether it's existence is
>>> RELEVANT?
>> 
>> We have shown how to do it with inkjet prints with pretty reasonable
>> certainty, and shown some proposed methodologies for doing so with chemical
>> prints.
> 
> I would have to think about chemical prints but yes I think that has been
> addressed convincingly. The noise floor is the variation in the paper
> base and the minimum discernible signal has also been defined.

John, Austin, 

Forgive me but what I saw was a theoretical basis for taking some
measurements, but without hypothetical realistic values there is no basis to
know if the result will have relevancy. John, correct me if I'm wrong, but
you even ended your description wondering if it would yield anything of
relevance. 

(No offense, but It also doesn't help that neither you or Austin restate
what definitions you are referring to. ;-)

Please humor me and make a demonstration for me, as I think this more than
anything else will clarify (for me) what this thread has been about.
Honestly, right now, I'm not sure.

Earlier today I spoke of a three print scenario, which I will restate:

> Lets consider a common situation we as photographers
> experience. Say through careful exposure and development we have a negative
> with a beautiful delicate distribution of tones throughout it's useful
> range. It would perfectly fit all it's tones on a given grade 2 paper. Let's
> say that print's density range would be 2 units. If we could measure the
> print on a pixel by pixel basis it would yield a perfect distribution of
> tones in a histogram, right to the ends with no clipping. We could then
> print that negative on a grade 3 paper, which may also yield a density range
> of 2 units, but we "clip" tones from the image on both ends due to increased
> contrast. It's histogram shows the clipping accordingly. We could even
> extend the scenario to where we keep the print on grade 3 paper, but dodge
> the shadows and burn the highlights, thus maintaining a higher internal
> contrast through the midtones, without clipping the ends. It's density range
> is still 2 units, and it's histogram looks more like the grade 2 print, at
> least at the ends.


Lets assume all of these prints were on a smooth glossy immaculate RC print,
which as expected, has minimal surface texture.

Please restate the formula each of you would apply to analyze the difference
in DyR between these three prints. Please plug into the formula as realistic
numbers as you can guesstimate for each print, and then show how you would
compare the results to make a meaningful conclusion about how and where the
prints differ. Finally, please be sure to fully address the difference in
"noise" between them, and explain how it has played a role in the different
DyR values recorded between them. Extra points will be given to a clear
verbal explanation, for the math impaired, throughout. ;-)

Please participate, I anxiously await your replies. I love the smell of
rubber hitting the road in the morning. ;-)

Todd

on 4/6/02 1:03 AM, Martin Wesley wrote:
 
> P.S. Since when do prints have pixels? <G>

Ain't terminology a bitch? ;-)

Todd

Martin,

> Todd,
> 
> I just want to point out that dynamic range in photography is generally
> discussed along with contrast. You don't need to get everything into a
> single value.

Okay, that makes it more useful.

I'm re-ordering your paragraphs a bit below, I hope you don't mind.

> What you mention below seems to be simply an issue of contrast. The response
> to exposure may become steeper or shallower depending upon the grade of the
> paper but once the print is a done deal the original grade is no longer a
> contributing factor. You are right and contrast is independent of density
> range and of what is commonly called dynamic range.

Yes, it's just an illustration of "internal" vs "external" contrast, but I
wanted to include an example where tones can be lost while maintaining
(max/external) contrast.
 
> Phil Davis discussed this at great length in "Beyond the Zone System" with
> lots of curves showing how Scene Brightness Range maps to the negative by
> way of the film's exposure response curve and how the negatives density
> range maps to the print by way of the paper's exposure response curve.

Yes, it sure takes curves to characterize a non-linear workflow.
 
> It is interesting that he manages to get through 200+ pages of photographic
> sensitometry and never even uses the term dynamic range.

Hmm.

> Austin is discussing an interesting relationship but it is not the
> relationship commonly called dynamic range in photography, i.e. the ratio of
> lightest and darkest which is frequently quantified as the density range. I
> believe that the property he is discussing is of interest but I don't see it
> as a new or expanded definition of this ratio.
 
> I have to agree with Roy that it serves little purpose to redefine dynamic
> range as something different than how it is commonly used in photography. I
> think that we would be better served at this point if there was a different
> term for the relationship Austin is describing. I know Austin will not like
> this but if the term dynamic range has already been appropriated, rightly or
> wrongly, trying to switch just adds to the confusion.

Again, no one is asking for a new interpretation of dynamic range, the
question (in my mind) is, has it been a long held interpretation for "some".

Jon Cone also uses "dynamic range" as Austin does. Now I know he's not an
engineer, so he may just be a pedestrian that by chance errs on the "wrong"
side of the word as Austin <G> (hey, Austin, should we disqualify him
because he's a pedestrian?), but Austin may not be alone out there:

<http://www.inkjetmall.com/store/long-dynamic-range.html>

"PiezographyBW has the longest dynamic range of any digital or traditional
process. This is a huge claim. However, film has a shorter dynamic range
than the human eye. Photographic paper has a shorter dynamic range than
film. The results of both can be plotted as an "S" curve in which the
highlight and shadows are subject to compression. PiezographyBW when used
with its internal tonal management system of ICQ profiles renders a perfect
linerization from dMax to dMin."


And we know he sure as heck CAN'T be talking about density range...
Todd

PS, If I look like I'm flopping from one side to the other on this I am.
Actually, for the moment I'm just thrashing around inside the issue, without
taking a side.

> Martin
> 
> P.S. Since when do prints have pixels? <G>
> 
> ----- Original Message -----
> From: "Todd Flashner" <tflash@...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Sent: Friday, April 05, 2002 3:16 PM
> Subject: Re: [Digital BW] Thoughts about Imaging
> 
> 
>> Roy,
>> 
>> I'm sensing that some of us have locked horns when we are probably more in
>> agreement than out of agreement. Perhaps if we all surrender a little
> ground
>> we can turn this back into a useful discussion.
>> 
>> Is it possible that *some* people used the term dynamic range to describe
>> something one step more complex than density range? I think behind
> Austin's
>> absolutist rhetoric that is what he's saying.
>> 
>> Working with my sense of logic, which doesn't prove anything, let's look
> at
>> the bigger picture. Lets consider a common situation we as photographers
>> experience. Say through careful exposure and development we have a
> negative
>> with a beautiful delicate distribution of tones throughout it's useful
>> range. It would perfectly fit all it's tones on a given grade 2 paper.
> Let's
>> say that print's density range would be 2 units. If we could measure the
>> print on a pixel by pixel basis it would yield a perfect distribution of
>> tones in a histogram, right to the ends with no clipping. We could then
>> print that negative on a grade 3 paper, which may also yield a density
> range
>> of 2 units, but we "clip" tones from the image on both ends due to
> increased
>> contrast. It's histogram shows the clipping accordingly. We could even
>> extend the scenario to where we keep the print on grade 3 paper, but dodge
>> the shadows and burn the highlights, thus maintaining a higher internal
>> contrast through the midtones, without clipping the ends. It's density
> range
>> is still 2 units, and it's histogram looks more like the grade 2 print, at
>> least at the ends.
>> 
>> Something *is* different in each of these prints, but it is not the
> density
>> range. Is it possible that some people would say that the grade 2 print
> had
>> a greater dynamic range than the straight grade 3 print, and that the
>> manipulated grade 3 print might have had the greatest dynamic range of the
>> three? If not dynamic range, what would be that term?
>> 
>> Todd
>> 
>> 
>> 
>> 
>> 
>>> --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin"
> <darkroom@i...>
>>> wrote:
>>>> Roy,
>>>> 
>>>>> So, how can we here is our niche, talk about coming up with a new
> idea,
>>>>> new concept of what "dynamic range" means?
>>>> 
>>>> No one is coming up with any new concepts...  "We" are merely pointing
> out
>>>> that the term has been "misapplied" in this "field", and that it
> attributes
>>>> a different property than, though is loosely related to, density range.
>>> 
>>> Austin,
>>> 
>>> I think Todd's "lost in the trees at points and loose sight of the
> woods"
>>> quote is right on.
>>> 
>>>> 
>>>>> We a just a part of a large
>>>>> community of imaging that long time ago has defined and has commonly
> used
>>>>> this term to mean sometime very specific.
>>>> 
>>>> Can you show evidence of this?
>>> 
>>> I think the Ansel Adams book and the Real World Scanning references were
>>> pretty relevant.  I'm glad to see you have read the scanning book.  You
>>> quoted one sentence that contained "dynamic range describes the actual
>>> limits of how many tones the scanner can really differentiate from light
> to
>>> dark".  You seem to be associating:  dynamic range <--> how many tones,
>>> when I think the real association is:  dynamic range <--> actual limits.
>>> Reading just this one sentence might be a little ambiguous, but read the
> whole
>>> paragraph.  Immediate following this sentence is the staircase example:
>>> dynamic range <--> height of staircase,  bit depth <--> number of steps.
>>> Later on he compares a scanner with "enormous dynamic range but only
>>> 256 steps" and a scanner with "lots of tiny steps and tiny dynamic
> range".
>>> There's no way to interpret these two examples to mean dynamic range
>>> is a measure of number of tones or steps!
>>> Do you wish to claim that this book and the three guys who wrote
>>> it are wrong and misuse and misdefine the term??
>>> 
>>> If you look at the Adam's book there's a diagram that explicitly shows
>>> "dynamic range".  He's talking about exposure and shows very clearly
>>> dynamic range going from about Zone I to Zone IX saying its the "useful"
>>> range of light values in the scene.  He even mentions how this dynamic
>>> range of light values maps directly into the range of "useful" densities
> on
>>> the negative.  Would you like to claim he's all wrong, too?
>>> 
>>> Please consider your position as it relates to these references.  These
>>> are both very explicit references to dynamic range as it relates to
> imaging.
>>> 
>>> Regards,
>>> Roy
>>> 
>>> 
>>>> 
>>> ... monitor stuff snipped
>>> 
>>>> 
>>>> Austin
>> 
>> 
>> 
>> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
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> 
> 
> 
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and other
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> 
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> 
> Please follow these basic guidelines:
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>

Hi Roy,

I am going to just snip indiscriminately and not say I did so ;-)

> From my point of
> view, your way made less intuitive sense than mine, but I perserved and
> tried to understand what the end result meant.  I.e.  could I
> conceptualize
> the quality or property so defined.  Mine is certainly pretty
> simple (in fact
> I think you believe its too simple).

Your statement of "the ratio of maximum contrast to minimum contrast" works
fine for me, where maximum contrast is (dMax - dMin), and I believe because
contrast requires two references, minimum contrast works all by it self with
no qualification, and that minimum can lie anywhere within the density
range.

> Anyway, given all that, I looked at a lot of the imaging
> literature and the
> descriptions of dynamic range all seem to agree with my view.

A LOT does, but not all.  That's why I am saying that it is an "old",
obviously deeply rooted, misconception...

> So here we are.  You've pretty much blown off all the "experts" in imaging
> saying they are not engineers and don't understand

Whoa there, leap of something...  I have not blown off ANY "IMAGING"
experts, but pointed out that the people referenced are PhotoShop EXPERTS,
which does NOT make them imaging experts.

> -- only audio experts
> know what this is all about.

Well, obviously some imaging experts (real ones who do hardware design) seem
to know all about it, and...it is also a very common concept in mechanical
engineering...where they view it exactly the same as I have described it (my
undergrad was ME, BTW).

> Minor question: If dynamic range is a measure of how many gray tones
> there are, how come its in dB and not just an integer.   Why doesn't
> it just say there are 237 grays in this image??

Good question.  As I've said, number is not a good term.  It (meaning
dynamic range) is a precept for "expanse" (which isn't a very good word
either, since dynamic range doesn't define the bounds, just what can go on
within bounds).  I really do have to get a better way to word this...but you
are right, calling it a hard number is not the intent, at least in the
analog world.  It IS a hard number in the digital world, simply because the
minimum discernable happens to be a hard number.

> Not that it matters much, but BSEE MIT, MSEE Stanford, My field has been
> mostly computer science.  Personally designed and personally
> written a ton of code.

[SIDEBAR] I used to give a lecture years ago called "Is Computer Science?",
later also one titled "Is Software Engineering".  We can get into that
discussion in some other lifetime ;-) They weren't as "bad" as you may take
their titles to be.  Their point was to separate out programming from
engineering, and get management types to understand they are not
(necessarily) the same.  This was at a time where programmers were called
"programmers"...and programming wasn't really part of any engineering
discipline, actually, any schools that taught programming did so as a part
of some other curriculum.  If they did have a degree program in
 "programming" it was called "computer science" and typically part of their
mathematics department, and not associated at all with engineering.  Also,
many astronomy and music graduates were now hired as programmers, and some
of them made damn good programmers in fact.

> You can probably claim more dynamic range usage in your specific area,
> but my diversity has served me well.

My background is also quite diverse as well...as well as in senior
engineering management for one a quite large computer company, and my share
of many startups, some quite successful, and some not.  I've been on both
sides of many coins.

> So you're asking how I think the English definition of "dynamic"
> is relevant to
> the technical definition??  I thought we were talking about a technical
> definition that was explicit and precise technically.  No?

Well, dynamic is a concept/understanding, and I believe it is entirely
applicable, and technically appropriate, to discuss a system in terms of it
being "dynamic".  Everyone else does ;-)

> Actually, the word I've equated "dynamic" to is "useful".  In
> ranges such as
> exposure, Zones, density.  The useful part of those ranges is where the
> image information is.  The part of the range is "dynamic", the
> parts outside
> are dead, useless, have no image.  Hence "dynamic" rather than "dead".
> Its just an English language analogy, but then that's all you asked for.

Well, useful seems to be more related to the endpoints/bounds than dynamic
is.  Dynamic, in and of it self, doesn't really care about the bounds,
except in calculating it, but after it's calculated, you can throw out the
bounds.  Useful, on the other hand, to me at least, seems to require the
bounds to be meaningful.

Two systems can have the same dynamic range, but have entirely different
"useful" ranges.  For example, positive and negative film.  The "useful"
range of positive film is much larger than the "useful" range of negative
film, if you are talking about density as the property...BUT...there are
more tones compressed within the smaller "useful" range of the negative film
then there are in the larger "useful" range of the positive film.

> I guess we're pretty much at an impasse.  Too bad.

For now ;-)  Well, I have more to come on this, as soon as I'm finished with
my discussions with some "others" on this subject.  So far, so good (for me
that is ;-).

> Sorry about any grumpy tone to this. I'm frustrated as I'm sure you are.

Why, thank you, I appreciate that very much.  I've tried to not be
frustrated...but I have been, no doubt...I'm sorry if I've come across as
arrogant and/or grumpy.  Please take any arrogance as confidence, not as
arrogance, and grumpy as, well, simply grumpy...but probably due more so to
lack of sleep with a sick dog, and two small children who want "up" at 11,
1, 3... ;-)

Regards,

Austin

--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:

> 
> Again, no one is asking for a new interpretation of dynamic range, the
> question (in my mind) is, has it been a long held interpretation for "some".
> 
> Jon Cone also uses "dynamic range" as Austin does. Now I know he's not an
> engineer, so he may just be a pedestrian that by chance errs on the "wrong"
> side of the word as Austin <G> (hey, Austin, should we disqualify him
> because he's a pedestrian?), but Austin may not be alone out there:
> 
> <http://www.inkjetmall.com/store/long-dynamic-range.html>
> 
> "Piezography*BW has the longest dynamic range of any digital or traditional
> process. This is a huge claim. However, film has a shorter dynamic range
> than the human eye. Photographic paper has a shorter dynamic range than
> film. The results of both can be plotted as an "S" curve in which the
> highlight and shadows are subject to compression. Piezography*BW when used
> with its internal tonal management system of ICQ profiles renders a perfect
> linerization from dMax to dMin."
> 
> 
> And we know he sure as heck CAN'T be talking about density range...
> Todd

Todd,

Nice quote.  Somehow I must have missed it looking around for dynamic range
references.  I wonder if anyone has enough rapport with him to get him to
say more, clarify "longer".

I'd like to take a stab at it though.  Naturally, I'm just reading what's quoted
and I just "interpreting" what I "think" he is saying and means.

One thing is that starts off referring to the DyR of the human eye and the DyR
of film.  The long DyR of the eye seems pretty analogous to just the range
of light that we can see -- the deep shadows are a "long" ways from the
"bright highlights".  Likewise the shorter DyR of the film is consistent and
analogous to the useful density range of the film.  So far I think this is basically
my intended interpretation.  (Its probably vague enough to come up with others).

Now he slips into the S-curve density curves -- saying "the highlights and shadows 
are subject to compression".  What is he trying to say??  Well I think he is saying
the end points are blocking up so that the density range of ordinary photo paper
that really has useful information is somewhat shorter that the total density range.
In other words, the "dynamic range" of ordinary photo paper is shorter because
of the S-curve nature rather that a linear nature i.e. the DyR doesn't really
go all the way out to dMin and dMax.  I think the next sentence
touting the linear nature of Piezo is saying that he considers the dynamic
range of Piezo to be longer because the linear section goes all the way out to
dMax and dMin.  I think a real key notion if that dynamic range always 
refers to the "useful" portion.  If we are talking about something with density
(film or paper) we should exclude densities that have no information.

I wonder if Cone would agree with my interpretation.

Roy

> I wonder if anyone has enough rapport with him to get him to
> say more, clarify "longer".

I will ask him.  I know both him and Bill.

Regards,

Austin

P.S.  I have to run now, but I do want to comment on your reply later...don'
t wait up for me though ;-)

Roy,

This si not correct, the National Fire Protection Association, Life Safety
Code 101 limits a riser height to no more than 7". So to obtain a riser
height of 7.5" would be a violation of national codes. ;-)

Mike


----- Original Message -----

From: "royvharrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, April 06, 2002 5:31 PM
Subject: Re: [Digital BW] Thoughts about Imaging


> If we wanted Height = 150 inches we could do:
> 150 = 25 * 6
> or
> 150 = 20 * 7.5

Hi Austin,

I've been thinking a bunch about all this and think
maybe I've got something new to add.

Although I felt that your audio signal processing references
were not obviously applicable, nonetheless they sure contain
a lot of mathematical and descriptive support for your
contention of dynamic range being equivalent to number of
bits of number of steps.  I'm not an audio signal processing
expert but I figured I need to get some idea what its about.

-------------------------------------------------------

To start I'd like to revisit the "staircase" model.  Just
to keep it out of the contention realm, lets imagine its
just a staircase in a building.

The most basic relationship is:
Height = NumSteps * StairRise

Pretty simple so let's put in some numbers:
Height = 10 feet = 120 inches
NumSteps = 20 steps
StairRise = 6 inches

Thus 120 = 20 * 6

If we wanted Height = 150 inches we could do:
150 = 25 * 6
or
150 = 20 * 7.5

The idea is: we have 3 variables (Height, Num, Rise) and we
can pick values that satisfy the equation.  However, there
just two independent variables and one dependent variable.
You certainly can pick any of the three variables to be
the dependent -- pick any values for the other two and
calculate the third.  (Obvious, but I just want to make sure
we're thinking the same.)

Now here comes the building department and they say the
building codes require all steps in the building to be the
same and fix it at 6 inches.  Now we have one constant,
one independent variable and one dependent variable.
For any staircase, you get to either pick the Height 
determining how many steps or you pick the number of steps
determining how high the stairs go.  You have only one
independent variable and you can completely characterize
any staircase with EITHER the Height or the NumSteps i.e.
they are "equivalent" descriptions.  Not the same numerical
number but the same information.

--------------

Now let's talk about audio systems. Just simple analog to start.

There are dB's (decibels) just about everywhere. In general
terms dB's are defined as: 10 log10 (power ratio).
  --reference from Higgin's same page as Dynamic Range.

Austin won't need this but others may wish to look at:
   http://www.phys.unsw.edu.au/~jw/dB.html

The important thing is that it compares two audio power levels
using a logarithmic scale.  E.G. every 3dB is a doubling or
halving of audio power. The other very important property
is how it relates to human perception of sound.  We perceive
loudness on basically the same scale.  Each increment of 
dB gives up an equivalent increment of perceived loudness.
The minimum discernable loudness different for humans is
somewhere around .5dB (I couldn't find an actual number so it
might be .4 or .3  or .6, but for the sake of argument I'll
keep using .5dB).  So every .5dB notch up we go gives the
different loudnesses we can hear.  Think about the high-end
amplifiers that instead of having a continuous volume 
control have a control that goes up in notches probably
labelled .5dB or 1dB at a time.  The great thing here is
that all the steps are perceived as the same size and that
size is directly related to human sound perception.

Another aspect of this, is that since dB is just a power
ratio, you can talk about a 3dB signal change anywhere in
the system.  It makes no difference if the 3dB is at the
input to the amp, inside, or at the output.  A dB is a dB
is a dB.  If you use dB values they are universal from
end to end in the audio system.

Now we define "dynamic range".  Again its just a dB measure
of the power ratio:  power of largest signal / power of the
smallest discernable signal.  "discernable" is important in
that we have to have some sound signal detectable above
the noise level -- otherwise you might be tempted to 
consider a totally zero signal that wouldn't do well in
the ratio :) .  If we come up with a 60dB number for DyR,
it means that the loudness sound is 60dB louder than the
quietest sound.  The kicker is that since all the dB's
are perceived equivalently we can say StepSize = .5dB,
Range = 60dB and voila: number of steps = 60/.5  = 120
different loudness levels.  With a fixed step size, the
dynamic range specifies both the Height and NumSteps.
Only one independent variable.

Austin, I hope you agree with all this.  It seems I've done
all this purely from the audio viewpoint.

Moving more quickly now to the digital signal processing
world, I don't know who designed DSP concepts and all their
motivations.  But if you are designing a digital system to 
mimic all the audio systems I describe above, it sure makes
sense to spec it such that you handle down to human
discernable levels and no further. You'd use number of
bits that fit the computer (16 usually) thus determining
number of steps, the step size would be the human reception
level (.5dB) and as the Higgin's shows on the very same
page we calculate the dynamic range. Really its just the
same as the analog with the addition 2^NumBits = NumSteps

I think all this agrees with your statements about
dynamic range.

-----------------------

Now let's look at it in the image world.  

To start: let's take a print with two grays that are very
close but just discernable.  For the sake of argument let's
say they differ in density by 0.03 log density units.  This
is the minimum discernable density step.  This print came
from a negative that has densities on it with in the printing
process produce the density step on the print.  What is the
density difference measured on the megative??  You can't
tell.  The print may have been made on a grade 1, a grade 3
or a grade 5 paper.  It the different cases you could come
up what the negative difference must have been.  Maybe
0.021 or 0.024 or 0.027.  The negative by itself cannot
tell you if the two tones on the print will be discernable.
This is very different than audio: a 3dB difference is
always a 3dB difference no matter what stage you look at.
On prints there is no notion of dB tonal difference.  Its
not a matter of it hasn't been defined yet. As shown in the
example its a matter of being impossible for the concept
to exist. The discernability changes from stage to stage
because of the very nature of how we do imaging.  (In fact
I think its even more intractable than that:  As Martin
observed a minimum discernable density on a single print
varies from the dark portions to the light portions.
Giving rise to the concept of Gamma.)

So for Imaging its just impossible to state one property
"dynamic range" and have it specify both the max /min
and the number of step (or number of bits).  My argument
basically goes back to the staircase model, with imaging
its a two independent variable system.  Whereas with
audio it was possible simplify the analysis to a one 
independent variable system.

---------------------

In our multitude of discussions, I never considered assuming
all the steps would be the same.  And I think your
extensive audio experience lead you to assume there
was "some" fixed step size.  Actually, more accurately, all
the formulas that you brought over had the fixed step
size builtin long, long ago -- no need to ever worry about
variable size steps in audio.

I think this is the root of all our collective confusion.
Maybe if we can agree on why we disagree, we can regroup
and agree to agree on a new view.

Regards,

Roy

Roy Harrington
roy@...
Black & White Photography Gallery
http://www.harrington.com

--- In DigitalBlackandWhiteThePrint@y..., "Michael Kravit" <michael.kravit@w...> wrote:
> Roy,
> 
> This si not correct, the National Fire Protection Association, Life Safety
> Code 101 limits a riser height to no more than 7". So to obtain a riser
> height of 7.5" would be a violation of national codes. ;-)
> 
> Mike

Hi Mike,

Is that a new code?  I designed and made a staircase about 12 years
ago.  I thought I remembered 8 inch max but that may have been for
non living areas like a basement.

My one claim to fame in woodworking:  my one and only staircase ever
was a solid oak, circular staircase in the entry of a big house.
curved over 90 degrees, hugged a curved wall on one side and with a
curved bannister on the other.

Fun project ONCE.  Paid for lots of woodworking tools!

Roy

Roy,

Not all that old, but it does not apply to residential buildings. Houses can
still go to 8" in some places, 7-3/4" in others.

Mike

> Hi Mike,
>
> Is that a new code?  I designed and made a staircase about 12 years
> ago.  I thought I remembered 8 inch max but that may have been for
> non living areas like a basement.
>
> My one claim to fame in woodworking:  my one and only staircase ever
> was a solid oak, circular staircase in the entry of a big house.
> curved over 90 degrees, hugged a curved wall on one side and with a
> curved bannister on the other.
>
> Fun project ONCE.  Paid for lots of woodworking tools!
>
> Roy

> Roy,
>
> This si not correct, the National Fire Protection Association, Life Safety
> Code 101 limits a riser height to no more than 7". So to obtain a riser
> height of 7.5" would be a violation of national codes. ;-)
>
> Mike

Mike,

Limits it for who?  Not for residential, at least in my state!  You can go
as high as 8".  I just finished doing a set of stairs...and it was 8", but
with the number of risers I had, we moved it down to 7 9/16 rise (9 1/2 run,
18 risers), and it's much more comfortable than it would have been with 8"
risers.

Here is an on-line calculator BTW:

http://www.daveosborne.com/dave/articles/staircalc.php?PHPSESSID=5f073a3276e
c46b29af476457552610f

Regards,

Austin

Care to explain the conection between this thread and Digital Black 
and White, the Print?
Other forums that I used to read got so far off topic that they are 
seldom read, if you would like to see a what I mean have a look at 
Qimage on Yahoo. Back in Dec there were over 1000 posts, last month 
there were little over 200. They got off topic, lead by a few 
people,  now the forum is not worth looking at.
Guys, why not use the email system of this kind of thread?

Barry
--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:
> > Roy,
> >
> > This si not correct, the National Fire Protection Association, 
Life Safety
> > Code 101 limits a riser height to no more than 7". So to obtain 
a riser
> > height of 7.5" would be a violation of national codes. ;-)
> >
> > Mike
> 
> Mike,
> 
> Limits it for who?  Not for residential, at least in my state!  
You can go
> as high as 8".  I just finished doing a set of stairs...and it was 
8", but
> with the number of risers I had, we moved it down to 7 9/16 rise 
(9 1/2 run,
> 18 risers), and it's much more comfortable than it would have been 
with 8"
> risers.
> 
> Here is an on-line calculator BTW:
> 
> http://www.daveosborne.com/dave/articles/staircalc.php?
PHPSESSID=5f073a3276e

> c46b29af476457552610f
> 
> Regards,
> 
> Austin

Austin,

The NFPA 101 applies to all buildings except most private residential. See
my other post.

Mike

----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, April 06, 2002 9:51 PM
Subject: RE: [Digital BW] Thoughts about Stairs... ;-)


> > Roy,
> >
> > This si not correct, the National Fire Protection Association, Life
Safety
> > Code 101 limits a riser height to no more than 7". So to obtain a riser
> > height of 7.5" would be a violation of national codes. ;-)
> >
> > Mike
>
> Mike,
>
> Limits it for who?  Not for residential, at least in my state!  You can go
> as high as 8".  I just finished doing a set of stairs...and it was 8", but
> with the number of risers I had, we moved it down to 7 9/16 rise (9 1/2
run,
> 18 risers), and it's much more comfortable than it would have been with 8"
> risers.
>
> Here is an on-line calculator BTW:
>
>
http://www.daveosborne.com/dave/articles/staircalc.php?PHPSESSID=5f073a3276e
> c46b29af476457552610f
>
> Regards,
>
> Austin
>
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
> - Include your full name with your message.
> - Include the address of your website, if you have one.
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - As the topic of a thread changes remember to change the subject header.
> - Good manners are required at all time. No personal attacks or "flames."
> - Complete your Yahoo profile.
> - Before posting a question, search the message archives and the various
resources on the homepage.

>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

Barry,

You are right, we have had 3 psots no off-topic. It strarted as as humor in
relation to Roy's stair-step comparison w/ dynamic range.

End of off-topic thread.
Unless of course we are photographing the stair in b/w. ;-)

Mike


----- Original Message -----
From: "flyfishingusa2002" <tflyfish@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, April 06, 2002 10:04 PM
Subject: Re: [Digital BW] Thoughts about Stairs... ;-)


> Care to explain the conection between this thread and Digital Black
> and White, the Print?
> Other forums that I used to read got so far off topic that they are
> seldom read, if you would like to see a what I mean have a look at
> Qimage on Yahoo. Back in Dec there were over 1000 posts, last month
> there were little over 200. They got off topic, lead by a few
> people,  now the forum is not worth looking at.
> Guys, why not use the email system of this kind of thread?
>
> Barry
> --- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin"
> <darkroom@i...> wrote:
> > > Roy,
> > >
> > > This si not correct, the National Fire Protection Association,
> Life Safety
> > > Code 101 limits a riser height to no more than 7". So to obtain
> a riser
> > > height of 7.5" would be a violation of national codes. ;-)
> > >
> > > Mike
> >
> > Mike,
> >
> > Limits it for who?  Not for residential, at least in my state!
> You can go
> > as high as 8".  I just finished doing a set of stairs...and it was
> 8", but
> > with the number of risers I had, we moved it down to 7 9/16 rise
> (9 1/2 run,
> > 18 risers), and it's much more comfortable than it would have been
> with 8"
> > risers.
> >
> > Here is an on-line calculator BTW:
> >
> > http://www.daveosborne.com/dave/articles/staircalc.php?
> PHPSESSID=5f073a3276e
> > c46b29af476457552610f
> >
> > Regards,
> >
> > Austin
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
> - Include your full name with your message.
> - Include the address of your website, if you have one.
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - As the topic of a thread changes remember to change the subject header.
> - Good manners are required at all time. No personal attacks or "flames."
> - Complete your Yahoo profile.
> - Before posting a question, search the message archives and the various
resources on the homepage.

>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

> In our multitude of discussions, I never considered assuming
> all the steps would be the same.  And I think your
> extensive audio experience lead you to assume there
> was "some" fixed step size.  Actually, more accurately, all
> the formulas that you brought over had the fixed step
> size builtin long, long ago -- no need to ever worry about
> variable size steps in audio.

Thanks for putting that into a useful perspective Roy. That spoke to the
concept on linearity vs non-linearity I kept referring to, but I don't think
I ever explained it in an understandable way. You did.

Todd

> If you use dB values they are universal from
> end to end in the audio system.

For any system you use dB for...not just audio.

> Now we define "dynamic range".  Again its just a dB measure
> of the power ratio:  power of largest signal / power of the
> smallest discernable signal.  "discernable" is important in
> that we have to have some sound signal detectable above
> the noise level -- otherwise you might be tempted to
> consider a totally zero signal

Not really, as noise will have some power level to it (it will never be 0 or
below 0), and therefore will be above zero.  As I've said, as noise
approaches zero, your dynamic range approaches infinity.

> If we come up with a 60dB number for DyR,
> it means that the loudness sound is 60dB louder than the
> quietest sound.

OK

> The kicker is that since all the dB's
> are perceived equivalently we can say StepSize = .5dB,
> Range = 60dB and voila: number of steps = 60/.5  = 120
> different loudness levels.

That works for me as far as I can tell...

> With a fixed step size, the
> dynamic range specifies both the Height and NumSteps.
> Only one independent variable.

Well, I'm not quite with you here.  Dynamic range, in and of it self, only
specifies the "number of relative steps"...it has no reference to the
height, in and of it self, as dB doesn't relate back to what you are
determining the dB of.  In other words, you measured voltage of, say 6V, and
a "stepsize" of .01V, you would have a dynamic range of X dB = 20 (for
audio) log10(6/.01) = ~55dB.  But, there is no way to get back to 6V or .01V
just by saying 55dB.

> Moving more quickly now to the digital signal processing
> world, I don't know who designed DSP concepts and all their
> motivations.  But if you are designing a digital system to
> mimic all the audio systems I describe above, it sure makes
> sense to spec it such that you handle down to human
> discernable levels and no further.

That's debatable...as there are nth order harmonics that DO effect the
audio...but we can ignore that for this discussion.

> You'd use number of
> bits that fit the computer (16 usually) thus determining
> number of steps, the step size would be the human reception
> level (.5dB) and as the Higgin's shows on the very same
> page we calculate the dynamic range. Really its just the
> same as the analog with the addition 2^NumBits = NumSteps
>
> I think all this agrees with your statements about
> dynamic range.

I'd say you might want to 2x that just to be above the Nyquist limit, as I
do believe it applies to any sensory system...

> -----------------------
>
> Now let's look at it in the image world.
>
> To start: let's take a print with two grays that are very
> close but just discernable.  For the sake of argument let's
> say they differ in density by 0.03 log density units.  This
> is the minimum discernable density step.  This print came
> from a negative that has densities on it with in the printing
> process produce the density step on the print.  What is the
> density difference measured on the megative??  You can't
> tell.

Correct, there is never any DIRECT backwards relationship from the print to
the negative, except for some sense of relativity.  In other words, you can'
t jump tones around...

> The print may have been made on a grade 1, a grade 3
> or a grade 5 paper.  It the different cases you could come
> up what the negative difference must have been.  Maybe
> 0.021 or 0.024 or 0.027.  The negative by itself cannot
> tell you if the two tones on the print will be discernable.

Correct.

> This is very different than audio: a 3dB difference is
> always a 3dB difference no matter what stage you look at.

Correct.

> On prints there is no notion of dB tonal difference.

Oh, I disagree with that.  I can measure the tones, and since dB is a
relative scale (as is density BTW ;-) that gives me dB.

> Its
> not a matter of it hasn't been defined yet. As shown in the
> example its a matter of being impossible for the concept
> to exist.

Well, I disagree with that, and can't see where you made that "leap".

> The discernability changes from stage to stage
> because of the very nature of how we do imaging.

It matters not that it changes from stage to stage, since the dynamic range
of each stage is entirely separate.  No one said it had to follow through
the process!

>  (In fact
> I think its even more intractable than that:  As Martin
> observed a minimum discernable density on a single print
> varies from the dark portions to the light portions.
> Giving rise to the concept of Gamma.)

Yes it does, but that doesn't mean it doesn't have dynamic range!  Dynamic
range, as I've said in other posts, does NOT mean the steps HAVE to be the
same.

> So for Imaging its just impossible to state one property
> "dynamic range" and have it specify both the max /min
> and the number of step (or number of bits).  My argument
> basically goes back to the staircase model, with imaging
> its a two independent variable system.  Whereas with
> audio it was possible simplify the analysis to a one
> independent variable system.

Ever hear of integration?  I brought exactly this variability up in a
previous post.  I take it you missed that?

> ---------------------
>
> In our multitude of discussions, I never considered assuming
> all the steps would be the same.

Neither had I ;-)

> And I think your
> extensive audio experience lead you to assume there
> was "some" fixed step size.  Actually, more accurately, all
> the formulas that you brought over had the fixed step
> size builtin long, long ago -- no need to ever worry about
> variable size steps in audio.

Correct, but those were simply for a concept...as I said above, and said in
other posts, that isn't difficult to deal with using calculus.

BTW, typically, in a system such as this, the "smallest discernable signal"
can be taken from the worst case, if you want a single value.  That's a
simple and dirty way to do it, but it, as you can well imagine, isn't the
best way to characterize a system.

> I think this is the root of all our collective confusion.
> Maybe if we can agree on why we disagree, we can regroup
> and agree to agree on a new view.

Well, I believe you have flaws in what you believed I believed, and that you
are also trying to carry "dynamic range" from step to step.  The dynamic
range of the film is entirely different than the dynamic range of the
scanner and then of the print.  They all have their own dynamic range in and
of themselves, and none of them are directly related to each other.


Regards,

Austin

> > In our multitude of discussions, I never considered assuming
> > all the steps would be the same.  And I think your
> > extensive audio experience lead you to assume there
> > was "some" fixed step size.  Actually, more accurately, all
> > the formulas that you brought over had the fixed step
> > size builtin long, long ago -- no need to ever worry about
> > variable size steps in audio.
>
> Thanks for putting that into a useful perspective Roy. That spoke to the
> concept on linearity vs non-linearity I kept referring to, but I
> don't think
> I ever explained it in an understandable way. You did.
>
> Todd

Todd,

We discussed this a number of posts ago:

"> You also did not speak to my premise that I think that a calculation of
> tones from DyR is only possible if linearity is assumed, which is not
> something I would take for granted in a silver print.

You don't need linearity at all.  Noise can be calculated using calculus,
and integrated over the entire range of the print...  Knowing math is not
your strong point?  I am guessing you don't know what integration is, in a
mathematical sense?  I can explain if you like."

And between you and I:

"> It would seem to me that those
> calculations work well for a system that produces a full and linear
> placement of tones between your dmin and dmax,

You are correct.

> but when those
> conditions are
> not met it would yield an inaccurate tone count. If I'm wrong
> please explain
> why.

You are absolutely right, and I'm happy that you have an understanding of
this to make such an observation!  Bravo!

This is where calculus comes into play.  It is a way of taking into account
the variability of the noise throughout the system.  Here's the deal.  The
noise "change" could be deterministic (possibly linear), which means it's
predictable.  If that is true (and I believe it is), then taking some number
of points (what ever are warranted by the type of equation that defines the
noise over the range, and if the noise is a simple gain, as in it's linear,
two points would do) in the "middle" will give you enough information to
derive the dynamic range.  Let's not talk about what that "result" or
equations would look like yet..."

Characterizing a non-linear system is just no big deal, it's done all the
time, and I've done it a number of times my self...

Regards,

Austin

Austin,

I'm working off your post below, but not in a counter point fashion for now.

We must keep in mind that in spite of the disjointed nature of the
discussion here there has been something of an ordered flow. However, I
believe as we digest the points of all participants in the discussion we
drop some of our convictions, and perhaps deepen others. At this point I'm
not sure of what your convictions are, so I'm not sure what from the past I
should or should not be speaking to.

For instance, at one point you were demonstrating how one could derive a
tone count from a few simple measures of a print. You were saying you could
determine how many shades of gray a print contained from an expression like
DyR of 3.7, or 25db. That condition I believe is only true if one assumes
that there are contiguous tones within the mediums range.

Remember, you had said DyR, and thus tone count, could be computed from a
measure of (dmax - dmin)/noise, and that noise could be determined from one
intermediary tone. That could give rise to a situation where a full tone
print could yield the same DyR as one which contained 4 tones. That flies in
the face of your tone count premise. Thus your interpretation of that
formula demanded linearity. What I mean by linearity here is that all tones
that could be contained within the density range ARE represented.

Let's look at the staircase. In the situation where you know the height of
the staircase (DnR), if the rise and depth of each step is the same
(linearity), you can measure just one step to determine how many steps are
present. This method is similar to your original description of the DyR
measuring method. If each step had a different rise and depth a calculation
based upon one step, which was different than all the others, could yield an
inaccurate result. Thus linearity IS required.

Furthermore, this also assumes that every step is in place. If some of the
middle steps have fallen, your calculation WILL be inaccurate!

Later, to address non-linearity you began to include the concept of
integration and calculus. For me to really understand this would take more
explanation than I deserve, but I sense you mean taking a broader sampling
of tones and noise and calculating them together. If so, fine.

But at that point I realized that by the time you've sampled the print
sufficiently to get meaningful representation across it's density range, it
would be wasteful to contract those measures into the DyR formula rather
than plot them as a curve or histogram, as has been the convention of
photography! Again, speaking not to the "could you", but "would you", of DyR
in a non-linear analog domain.

This question of relevance is one that Martin brought up days and dozens of
posts ago, and which speaks to the whole premise of why DyR is used
differently in the field of photography than audio or digital.

Perhaps if/when you summarize what you presently maintain on the issue and
what you've dropped, and/or present an explanation of how you would approach
my three print challenge, I will know what you still maintain - or perhaps
you can convince me I'm wrong. Either way, I think we're loosing sight of
context.

Todd

> Todd,
> 
> We discussed this a number of posts ago:
> 
>> You also did not speak to my premise that I think that a calculation of
>> tones from DyR is only possible if linearity is assumed, which is not
>> something I would take for granted in a silver print.
> 
> You don't need linearity at all.  Noise can be calculated using calculus,
> and integrated over the entire range of the print...  Knowing math is not
> your strong point?  I am guessing you don't know what integration is, in a
> mathematical sense?  I can explain if you like."
> 
> And between you and I:
> 
> "> It would seem to me that those
>> calculations work well for a system that produces a full and linear
>> placement of tones between your dmin and dmax,
> 
> You are correct.
> 
>> but when those
>> conditions are
>> not met it would yield an inaccurate tone count. If I'm wrong
>> please explain
>> why.
> 
> You are absolutely right, and I'm happy that you have an understanding of
> this to make such an observation!  Bravo!
> 
> This is where calculus comes into play.  It is a way of taking into account
> the variability of the noise throughout the system.  Here's the deal.  The
> noise "change" could be deterministic (possibly linear), which means it's
> predictable.  If that is true (and I believe it is), then taking some number
> of points (what ever are warranted by the type of equation that defines the
> noise over the range, and if the noise is a simple gain, as in it's linear,
> two points would do) in the "middle" will give you enough information to
> derive the dynamic range.  Let's not talk about what that "result" or
> equations would look like yet..."
> 
> Characterizing a non-linear system is just no big deal, it's done all the
> time, and I've done it a number of times my self...

Hi Todd,

> Remember, you had said DyR, and thus tone count, could be computed from a
> measure of (dmax - dmin)/noise, and that noise could be
> determined from one
> intermediary tone.

That will give you a good idea of the dynamic range, yes.

> That could give rise to a situation where a full tone
> print could yield the same DyR as one which contained 4 tones.

That is true, even a print with one tone could have the same dynamic range
as one with a thousand tones (providing they were printed with exactly the
same system/paper etc.).  Dynamic range is a measure of what is possible
within the density range, as limited by "noise", not what only exists.

> That flies in
> the face of your tone count premise.

I don't believe so.

> Thus your interpretation of that
> formula demanded linearity. What I mean by linearity here is that
> all tones
> that could be contained within the density range ARE represented.

Not at all.

> Let's look at the staircase. In the situation where you know the height of
> the staircase (DnR), if the rise and depth of each step is the same
> (linearity), you can measure just one step to determine how many steps are
> present.

Correct.

> This method is similar to your original description of the DyR
> measuring method. If each step had a different rise and depth a
> calculation
> based upon one step, which was different than all the others,
> could yield an
> inaccurate result. Thus linearity IS required.

Not at all.  If the noise can be characterized, which it can, then it's easy
to get a very accurate result.

> Furthermore, this also assumes that every step is in place. If some of the
> middle steps have fallen, your calculation WILL be inaccurate!

Not at all.  Integration takes care of this (kind of like interpolation).
If the characteristic of the "noise" is consistent, you can derive the noise
at any point.

> Later, to address non-linearity you began to include the concept of
> integration and calculus. For me to really understand this would take more
> explanation than I deserve, but I sense you mean taking a broader sampling
> of tones and noise and calculating them together. If so, fine.

Yes.

> Perhaps if/when you summarize what you presently maintain on the issue and
> what you've dropped, and/or present an explanation of how you
> would approach
> my three print challenge...

I have actually strongly considered really writing this up, and subjecting
it to peer review.  When I have the time in a few months, and my new lab is
set-up, I'll not only have the space, but hopefully the time, to give this a
thorough write-up with 8x10 color glossy photographs with circles and arrows
on the back of each one ;-)

Regards,

Austin

on 4/7/02 3:13 PM, Austin Franklin wrote:

>> That could give rise to a situation where a full tone
>> print could yield the same DyR as one which contained 4 tones.
> 
> That is true, even a print with one tone could have the same dynamic range
> as one with a thousand tones (providing they were printed with exactly the
> same system/paper etc.).  Dynamic range is a measure of what is possible
> within the density range, as limited by "noise", not what only exists.
 
>> That flies in
>> the face of your tone count premise.
> 
> I don't believe so.

Austin

Whelp, I see no reason to go further with this.

I suggest a comparison between a paper that is capable of only four tones,
lets say two highlight tones, and two shadow tones, with no midtones, Vs a
paper that is capable of thousands of linearly written tones throughout. If
the two share the same density range and noise, they will yield the same DyR
formula.

If you are okay with that, and suggest DyR still yields a reasonable
indicator of tone count, and aren't willing to reconcile the obvious breech
of logic, I give up.

I've asked you on several occasions to demonstrate how you would apply your
formula to confusing scenarios, and so far you have not. It's clear we are
at an impasse you are not willing or able to resolve as yet, so until that
time my efforts to understand or to further this conversation will be in
vain.

I look forward to what you have to say in a few months.

Todd

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> 
> > The kicker is that since all the dB's
> > are perceived equivalently we can say StepSize = .5dB,
> > Range = 60dB and voila: number of steps = 60/.5  = 120
> > different loudness levels.
> 
> That works for me as far as I can tell...
> 
> > With a fixed step size, the
> > dynamic range specifies both the Height and NumSteps.
> > Only one independent variable.
> 
> Well, I'm not quite with you here.  Dynamic range, in and of it self, only
> specifies the "number of relative steps"...it has no reference to the
> height, in and of it self, as dB doesn't relate back to what you are
> determining the dB of.  In other words, you measured voltage of, say 6V, and
> a "stepsize" of .01V, you would have a dynamic range of X dB = 20 (for
> audio) log10(6/.01) = ~55dB.  But, there is no way to get back to 6V or .01V
> just by saying 55dB.
> 

Well, well, well, Austin, its good to see these two paragraphs together.
The fallacy of your logic, your feeling of the whole dynamic range concept
is well illustrated here.  I'm sure you've been able to do your job for years.
Plugging in numbers is NOT the same understanding and feeling the concept.

Let's also add the formula:   DynRange = 10 * log10 (maxpower/minpower)
 and yes, maxpower = power of maximum signal 
 and  minpower i= power of minimum discernable signal

The basic fallacy is the mixing of linear scales and exponential (or geometric)
scales --  especially as it relates to "What is a step?".  In the real world just
about every ordinary human experience "feels" linear.  There's no difficulty
thinking of a 1 foot ruler and saying there's a 1 inch step so 12/1 = 12 steps
or 12 inches -- its so basic it seems absurd to even say it.   You are
looking at the DynRange formula and seeing the term (maxpower/minpower)
and "feeling"  that its the same thing as the ruler.  Its like minpower is the
step size and when you divide it into maxpower you get "how many steps".
This is exactly what you've said in the second paragraph above.
This is completely wrong as a concept.  Why?? Because power is an
exponential scale from a perceptual point of view.  I.E.  To get a "linear" feel
of loudness in the audio system, the power output has to go up exponentially.

Here's a short audio example:
We have an audio amplifier -- puts out 100 watts at the max end, and measuring
the low end (smallest discernable signal) we get 1 watt.    Let's throw that
into the DynRange formula:  the inside term is (100/1), you are thinking that
this is 100 steps.  Not TRUE!!
This would mean the steps would be:
1,2,3,4,5,6,7,8 ...95, 96, 97, 98, 99, 100  watts
but these steps make no sense, the intervals in the beginning are huge and
the ones at the end are miniscule.

The steps have to be like:
1, 2, 4, 8, 16, 32, 64
or
1, 3, 9, 27, 81
or
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 ....

Each of these sequencies produce and "even" set of intervals or steps.   Also
notice they all  have a different number of steps --- the original statement
100 watt -- 1 watt spec says nothing whatsoever about number of steps.
Just like a staircase going from floor 1 to 2, can be built with any number of
steps -- you just have to pick an appropriate step size.

Bottom line: In a exponential scale, a step is always a ratio, a range is
always a ratio.  StepRatio ^ NumSteps = RangeRatio

Yeah, but ...  What about the first paragraph?  Here I said:
Range = 60dB, Stepsize = 0.5dB  and then I calculated (60dB/.5dB)
getting 120 levels or steps.  Isn't this what I just argued against??
NO, not at all.  The reason is dB's are a linear scale so the ruler analogy
works just fine.  dB's are the log of an exponential scale.  Taking the log
converts an exponetial scale to a linear scale.  We as human beings use
this conversion all the time because we are so much more comfortable
having an intuitive feel for a linear scale.

This is pure and simple mathematical transformation.   There's no hand
waving arguments --- logs are defined very precisely.

Here's probably the most basic of log transformations:
log (A*B) = log(A) + log(B)
log (A/B)  = log(A) - log(B)

Look at these two terms:

log10 (max/min)    <<<<NOT EQUAL>>>>     log10(max)/log10(min)

The left side is the dynamic range term.  The right side is the number
of steps example and calculation.  Austin, although you've always punched
in the calcs like the left side, but you are thinking (feeling) like the right side.
It's produced a desire on your part to keep trying to get the same
"feeling" in Imaging but that has distorted your transformation from 
the audio world to the imaging world.

Taking the DynRange formula and transforming it a little:

DyR = 10 * log10 (maxpower/minpower)
DyR = 10 * (log10(maxpower) - log10(minpower))
DyR = ( 10*log10(maxpower)  - 10*log10(minpower))

Imagine measuring maxpower and stating it as a db relative to a standard,
let's call it maxdb.  Similarly, minpower as a db relative to the same 
standard, calling it mindb.  If   this isn't clear, check:
         http://www.phys.unsw.edu.au/~jw/dB.html

See now have:
DyR  = maxdb - mindb

Example:   connect the dbmeter on amp at full power -- reads 40dB
 with amp at min power -- read -20dB

So, DyR = 40dB - (-20db)  = 60dB

QED

All things called "ranges" are just a top end and a bottom end.  No more,
no "internal" information whatsoever.  "Range" can apply to a linear
scale and the size of the range = max - min.   "Range" can also apply
to an exponential scale, then the size of the range = max / min.
An exponential range can be converted to a linear range by taking the log.
A linear range can be converted to an exponential range by putting it in
the exponent.

Dynamic range is a range just like any other range,  the word "dynamic"
is just a qualifier that says "perceptually interesting part of".

In photography, we can "dynamic range" various different parts.  Some
of them are exponential scales like exposure, some have been linearized
by taking the log like density.   The concept of "stops" is also a linearized
form of the exposure range.

-------

Roy

Hi, Oh Prolific Roy ;-)

> > > The kicker is that since all the dB's
> > > are perceived equivalently we can say StepSize = .5dB,
> > > Range = 60dB and voila: number of steps = 60/.5  = 120
> > > different loudness levels.
> >
> > That works for me as far as I can tell...
> >
> > > With a fixed step size, the
> > > dynamic range specifies both the Height and NumSteps.
> > > Only one independent variable.
> >
> > Well, I'm not quite with you here.  Dynamic range, in and of it
> self, only
> > specifies the "number of relative steps"...it has no reference to the
> > height, in and of it self, as dB doesn't relate back to what you are
> > determining the dB of.  In other words, you measured voltage
> of, say 6V, and
> > a "stepsize" of .01V, you would have a dynamic range of X dB = 20 (for
> > audio) log10(6/.01) = ~55dB.  But, there is no way to get back
> to 6V or .01V
> > just by saying 55dB.
> >
>
> Well, well, well, Austin, its good to see these two paragraphs together.
> The fallacy of your logic, your feeling of the whole dynamic range concept
> is well illustrated here.  I'm sure you've been able to do your
> job for years.
> Plugging in numbers is NOT the same understanding and feeling the concept.

Whether you believe it or not, I just don't plug in the numbers, I do
completely understand the concept of dynamic range...and we'll see if that
bears out ;-)

dB (as in the result of a dynamic range equation) does not translate back to
"Height" and "NumSteps", dB is merely a relative scale of power.  You could
have an absolute range of 1V with the exact same dynamic range as a range
with 100V, the "heights" as you call them, are entirely different.
Relatively, yes, the max/min are the same...but as I said, there is NO way
to get back to the original hard (as in actual values, not relative values)
from dB.  That's simple fact.

> The basic fallacy is the mixing of linear scales and exponential
> (or geometric)
> scales

Er, I didn't mix them anywhere...but you're right, that would be a
fallacy...

> You are
> looking at the DynRange formula and seeing the term (maxpower/minpower)
> and "feeling"  that its the same thing as the ruler.

The example of a ruler is fine, providing you understand what it means.  In
the example I've cited above using 6V/.01V, no matter where you are on the
scale, you can only measure to .01V.

Now, using a ruler for your example of power.  As an aside, every 3db is a
doubling of power, not 2x the dB value...but that may not matter...it
depends on what "unit" your measurement is in.  If you ARE measuring in dB
(which I would assume you would have to do to give two numbers like 60dB as
your largest swing, and .5dB as your minimum discernable), and your
measurements are in fact only accurate to a certain dB level (as your
example above), then a ruler works fine also.

Just as an aside note, in audio, just because you have doubled power, you do
NOT get double the "loudness".  That takes ~10x to double the loudness.

The fallacy would be applying steps of "hard" numbers to a power system, and
vice versa.  It doesn't work.  You couldn't say you had a max of 60dB and a
step of .01V.  Both numbers have to stay in the same measurement system
(unit).

> Its like
> minpower is the
> step size and when you divide it into maxpower you get "how many steps".

If you are measuring in power, then that works fine.

> This is exactly what you've said in the second paragraph above.

Actually, I used volts, not power, but it does still apply.

> This is completely wrong as a concept.  Why?? Because power is an
> exponential scale from a perceptual point of view.

It doesn't matter.  All that matters is that you understand what your
"system" is, and what you are measuring in.  Typically, minimum measurable
of a system is in the same "units" as the system you are measuring...  If it
's power, then it's power.  If it's volts, then it's volts.  Exponential
system or not...  That appears to a possible source of your confusion.

> I.E.  To get
> a "linear" feel
> of loudness in the audio system, the power output has to go up
> exponentially.

Correct.

> Here's a short audio example:
> We have an audio amplifier -- puts out 100 watts at the max end,
> and measuring
> the low end (smallest discernable signal) we get 1 watt.

A power output of 1 watt at the low end does not necessarily mean you have a
smallest discernable signal of 1 watt, BTW, but I'm fine with that number,
as it really doesn't matter.

> Let's
> throw that
> into the DynRange formula:  the inside term is (100/1), you are
> thinking that
> this is 100 steps.  Not TRUE!!

It certainly IS true, IF your measuring device is accurate to only 1 watt,
as YOU specified above, and you ARE measuring watts...  YOU seem to be
confusing systems here.  What ever your measuring system is, you are only as
accurate as the measuring system is...and if your measurement system gives
measurements in some log form (as a densitometer does, for example, or a
sound pressure level meter), then your steps are also in log form.

BUT if you are measuring in "loudness", well, then, you can't very well give
"watts" as your unit, as watts is NOT the same relative measurement of
"loudness".  I believe that is a clear mistake.

<big snip>

> See now have:
> DyR  = maxdb - mindb

Sure, note both are in dB.  Nothing wrong with that.  BUT...if you are
trying to claim somehow that has something to do with density range, it does
not!  Density measurements are NOT in dB, period.

> Example:   connect the dbmeter on amp at full power -- reads 40dB
> with amp at min power -- read -20dB
>
> So, DyR = 40dB - (-20db)  = 60dB
>
> QED

Yeah, I could say 1+1=2 QED, but your "claim" has to be applicable to what
the discussion is.  The arithmetic in your example is correct, but your
example has nothing to do with photographic density range being the same as
dynamic range.  As I've said countless times, because density values are in
a logarithmic scale, it does not mean they are the same as dB (which are
also in a logarithmic scale), and therefore density range is absolutely NOT
the same as dynamic range.

> All things called "ranges" are just a top end and a bottom end.

Correct, but then add the word "dynamic" to it, and adds another dimension
to the meaning, or why even bother adding it...especially considering
dynamic means "characterized by continuous change".  That hardly seems
applicable to two static numbers!

> Dynamic range is a range just like any other range,  the word "dynamic"
> is just a qualifier that says "perceptually interesting part of".

I don't mean to be snide, but that's just silly.  So many things have ranges
specified, and they aren't called "dynamic ranges", but they are the range
within which the device operates.  In fact, many specs include both a range
of operation, and a dynamic range.

BTW, things can only be perceived if you can "perceive" a difference, which
fits perfectly with what I've said ;-)

If I get one of THE "gurus" to say that "dynamic range is NOT the same as
density range" will you give?  You're on a crusade to prove something wrong
that isn't wrong, and you aren't going to be able to do it ;-)

Regards,

Austin

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Hi, Oh Prolific Roy ;-)
> 

Gee, Thanks for the moniker.

There seems to be a few instances of disagreements about whether we're
talking about linear versus exponential.  Its usually an issue of what units
and what measuring device.  Before going into the details, let me say that
I'm always referring to a scale as it relates to human perception.  Certainly
its OK to use an electronic device for measuring the number but I always
want to relate it back to how we will perceive it.  For example, dB's are
linear because we hear it linear as well.  Amp wattage is exponential because
we need exponential increases in wattage to produce linear perception.
The examples that have no "human" connection are kind of up for grabs
so I think it'd be best to avoid them (or be explicit).

> 
> dB (as in the result of a dynamic range equation) does not translate back to
> "Height" and "NumSteps", dB is merely a relative scale of power. 
OK.

  You could
> have an absolute range of 1V with the exact same dynamic range as a range
> with 100V, the "heights" as you call them, are entirely different.
?? not sure what's stated here

> Relatively, yes, the max/min are the same...but as I said, there is NO way
> to get back to the original hard (as in actual values, not relative values)
> from dB.  That's simple fact.

Sure, specifying the size a range whether exponential or linear never tells 
the absolute endpoints -- just relative to each other.
ExponRange = Max / Min
or
LinearRange = Max - Min
-- neither range value tells the absolutes.

> 
> > The basic fallacy is the mixing of linear scales and exponential
> > (or geometric)
> > scales
> 
> Er, I didn't mix them anywhere...but you're right, that would be a
> fallacy...
My main point goes back to using the "scale" (expon or linear) as
defined by the human not by the measuring device.

> 
> > You are
> > looking at the DynRange formula and seeing the term (maxpower/minpower)
> > and "feeling"  that its the same thing as the ruler.
> 
> The example of a ruler is fine, providing you understand what it means.  In
> the example I've cited above using 6V/.01V, no matter where you are on the
> scale, you can only measure to .01V.
Seems like there isn't human factor here, saying you can measure 0.01V,
sounds like everything is linear.

> 
> Now, using a ruler for your example of power.  As an aside, every 3db is a
> doubling of power, not 2x the dB value...but that may not matter...it
Yes, the dB unit would always be linear scale in my mind.
> depends on what "unit" your measurement is in.  If you ARE measuring in dB
> (which I would assume you would have to do to give two numbers like 60dB as
> your largest swing, and .5dB as your minimum discernable), and your
> measurements are in fact only accurate to a certain dB level (as your
> example above), then a ruler works fine also.
> 
> Just as an aside note, in audio, just because you have doubled power, you do
> NOT get double the "loudness".  That takes ~10x to double the loudness.
I'm not sure if this is a direct response to something I wrote.  I'm really
only interested in saying power is exponential, and I'll stick to using "loudness"
just as a descriptive term.

> 
> The fallacy would be applying steps of "hard" numbers to a power system, and
> vice versa.  It doesn't work.  You couldn't say you had a max of 60dB and a
> step of .01V.  Both numbers have to stay in the same measurement system
> (unit).
Sure, can't mix units.

> 
> > Its like
> > minpower is the
> > step size and when you divide it into maxpower you get "how many steps".
> 
> If you are measuring in power, then that works fine.
> 
> > This is exactly what you've said in the second paragraph above.
> 
> Actually, I used volts, not power, but it does still apply.
> 
> > This is completely wrong as a concept.  Why?? Because power is an
> > exponential scale from a perceptual point of view.
> 
> It doesn't matter.  All that matters is that you understand what your
> "system" is, and what you are measuring in.  Typically, minimum measurable
> of a system is in the same "units" as the system you are measuring...  If it
> 's power, then it's power.  If it's volts, then it's volts.  Exponential
I know power = volts^2 so either is OK.  
> system or not...  That appears to a possible source of your confusion.
> 
> > I.E.  To get
> > a "linear" feel
> > of loudness in the audio system, the power output has to go up
> > exponentially.
> 
> Correct.

For the last couple of paragraphs, I think you agree that "power" in the
audio sense is an exponential scale.  It looks like you are also maintaining
that  (maxpower/minpower)  has a "how many steps" meaning.
This, to me, is the crucial point in this whole discussion.  Its a purely
mathematical issue that for an exponential scale, the max/min ratio
is just a size of the total range.  There's no meaning of step here.
I thought my different of exponential series in the last post clearly
demonstated that.  


> 
> > Here's a short audio example:
> > We have an audio amplifier -- puts out 100 watts at the max end,
> > and measuring
> > the low end (smallest discernable signal) we get 1 watt.
> 
> A power output of 1 watt at the low end does not necessarily mean you have a
> smallest discernable signal of 1 watt, BTW, but I'm fine with that number,
> as it really doesn't matter.
> 
> > Let's
> > throw that
> > into the DynRange formula:  the inside term is (100/1), you are
> > thinking that
> > this is 100 steps.  Not TRUE!!
> 
> It certainly IS true, IF your measuring device is accurate to only 1 watt,
> as YOU specified above, and you ARE measuring watts...  YOU seem to be
> confusing systems here.  What ever your measuring system is, you are only as
> accurate as the measuring system is...and if your measurement system gives
> measurements in some log form (as a densitometer does, for example, or a
> sound pressure level meter), then your steps are also in log form.
> 
> BUT if you are measuring in "loudness", well, then, you can't very well give
> "watts" as your unit, as watts is NOT the same relative measurement of
> "loudness".  I believe that is a clear mistake.
You can use watts its just that you have to think in exponential series.
This is the point with the various series that I wrote earlier.

> 
> <big snip>
> 
> > See now have:
> > DyR  = maxdb - mindb
> 
> Sure, note both are in dB.  Nothing wrong with that.
My point here was to mathematically change equation and show
it no longer has the divide that (at least I'm surmising) makes the
original form of equation look like "number of steps".


  BUT...if you are
> trying to claim somehow that has something to do with density range, it does
> not!  Density measurements are NOT in dB, period.
Well, yes, density and dB are different.  But I'm glad you noticed the
hint of them having some parallelism.  Mathematically they sure do
look a lot alike, don't they?

Say we had a series of audio powers:
1,  1/2, 1/4, 1/8, 1/16 ...
this would correspond to decreasing dB's:
0, 3, 6, 9, 12, 15 ...

Similarly, we had a series of light intensities:
1,  1/2, 1/4, 1/8, 1/16 ...
this would correspond to densities of:
0, .3, .6, .9, 1.2, 1.5, ...

I'd sure like an awful good reason to think all this parallelism
should be ignored.  If you have a reason, please do tell.

> 
> > All things called "ranges" are just a top end and a bottom end.
> 
> Correct, but then add the word "dynamic" to it, and adds another dimension
I like it still to be a range -- great to add more qualification (isn't that
what adjectives do?).

> to the meaning, or why even bother adding it...especially considering
> dynamic means "characterized by continuous change".  That hardly seems

Well, at least we both have cute quotes now :).   I'm going to have to keep
asking what's "continuously changing".

> applicable to two static numbers!
Aren't your maxpower and minpower measurements basically a "static" numbers.
What are you calling "continuous change"?   I don't see any "continuous
change" when you measure the power amp and a certainly do see any
continuous change when you get to the photo print. 

Are you thinking of the sinewave change of the audio signal?  But you don't
perceive changes in the constant tone.  I guess if you wanted you could
also claim sinewave electromagnetic radiation i.e. light, but you don't
perceive that either.

> 
> > Dynamic range is a range just like any other range,  the word "dynamic"
> > is just a qualifier that says "perceptually interesting part of".
> 
> I don't mean to be snide, but that's just silly.  So many things have ranges
> specified, and they aren't called "dynamic ranges", 
I didn't say all  ranges are dynamic.  I said a "dynamic range" is firstmost
a range and it ought to AT LEAST have the notion of being a range.
The "dynamic" is an ADDITIONAL modifier, qualifying additional limits.

   but they are the range
> within which the device operates.  In fact, many specs include both a range
> of operation, and a dynamic range.

Well we're not looking at the same spec sheet, but it sounds like the range
of operation is the total range where you don't fry the components,
whereas the dynamic range is were the device works "well" i.e. meets the
specs of what it is supposed to do.

> 
> BTW, things can only be perceived if you can "perceive" a difference, which
> fits perfectly with what I've said ;-)
> 
> If I get one of THE "gurus" 
   You think there's any chance of defining "guru"?  :)   If there are gurus 
shouldn't they have a book?  Didn't we fail to agree on any books that either
of us found?

  to say that "dynamic range is NOT the same as
> density range" will you give?

Actually, I love hear somebody else say something about it all.  

   Well it seems that if we're defining DynRange of
something whose key property is density, we ought to end of with some kind
of range whose units are density.  I not saying the DynRange has to be
identical to the total density range -- but it ought to  be some subset.
Similarly you could be talking about the DynRange of a natural
scene --  density wouldn't be to useful since there isn't any.  Here
you ought to use whatever units you can measure.  (My spotmeter does
EV at ISO 100 for instance, so I'd be thinking of DynRange in EV's).

  You're on a crusade to prove something wrong
> that isn't wrong, and you aren't going to be able to do it ;-)
Well somebody is :)

> 
> Regards,
> 
> Austin

Here we go again.

Roy

> Before going into the details, let me say that
> I'm always referring to a scale as it relates to human
> perception.

But not all sensors sense in "human perception" units...so I believe that is
going to cause some confusion.

> >
> > > The basic fallacy is the mixing of linear scales and exponential
> > > (or geometric)
> > > scales
> >
> > Er, I didn't mix them anywhere...but you're right, that would be a
> > fallacy...
> My main point goes back to using the "scale" (expon or linear) as
> defined by the human not by the measuring device.

I don't see how that matters.  Scale can be applied to either equally as
correctly.

> > > You are
> > > looking at the DynRange formula and seeing the term
> (maxpower/minpower)
> > > and "feeling"  that its the same thing as the ruler.
> >
> > The example of a ruler is fine, providing you understand what
> it means.  In
> > the example I've cited above using 6V/.01V, no matter where you
> are on the
> > scale, you can only measure to .01V.
>
> Seems like there isn't human factor here, saying you can measure 0.01V,
> sounds like everything is linear.

That doesn't matter, as it relates to dynamic range...which is what this
conversation is about.  The next paragraph (which I clipped) showed an
example using power.  Ruler works for either linear or logarithmic it doesn'
t matter...

> > Just as an aside note, in audio, just because you have doubled power,
you do
> > NOT get double the "loudness".  That takes ~10x to double the loudness.
>
> I'm really
> only interested in saying power is exponential, and I'll stick to
> using "loudness"
> just as a descriptive term.

Yes, but the "scale" watts is different than the "scale" that loudness and
you can't interchange the two in a linear fashion...

> For the last couple of paragraphs, I think you agree that "power" in the
> audio sense is an exponential scale.  It looks like you are also
> maintaining
> that  (maxpower/minpower)  has a "how many steps" meaning.
> This, to me, is the crucial point in this whole discussion.  Its a purely
> mathematical issue that for an exponential scale, the max/min ratio
> is just a size of the total range.  There's no meaning of step here.
> I thought my different of exponential series in the last post clearly
> demonstated that.

It did not.  You can determine the dynamic range of ANYTHING that has a
largest absolute signal, and a smallest discernable signal, even if that is
in dB!

Sound pressure level meter spec: Range: 20-120dB, noise: 2dB.

Dynamic range 10log10(100/2) or 17dB, which is the same as 10**1.7, or 50...

> > BUT if you are measuring in "loudness", well, then, you can't
> very well give
> > "watts" as your unit, as watts is NOT the same relative measurement of
> > "loudness".  I believe that is a clear mistake.
> You can use watts its just that you have to think in exponential series.
> This is the point with the various series that I wrote earlier.

Sure, you can use watts, and sure you can use loudness...but you can't mix
the two.  They are different scales.

> >
> > <big snip>
> >
> > > See now have:
> > > DyR  = maxdb - mindb
> >
> > Sure, note both are in dB.  Nothing wrong with that.
> My point here was to mathematically change equation and show
> it no longer has the divide that (at least I'm surmising) makes the
> original form of equation look like "number of steps".

Well, perhaps I misunderstood what you were trying to get at, then I'll have
to say that your equation is wrong...if you are using an example like I used
with the sound pressure level spec...the dynamic range of that device IS NOT
100 - 2, it is as I stated it.

>   BUT...if you are
> > trying to claim somehow that has something to do with density
> range, it does
> > not!  Density measurements are NOT in dB, period.
> Well, yes, density and dB are different.  But I'm glad you noticed the
> hint of them having some parallelism.

NOTICED THE HINT?  I've said this all along, and known it long before
conversing with you about that.  Thanks, but I didn't need a "hint".

> Mathematically they sure do
> look a lot alike, don't they?

Yeah, but that isn't relevant for anything as far as our discussion goes.

> I'd sure like an awful good reason to think all this parallelism
> should be ignored.  If you have a reason, please do tell.

Because it isn't relevant in this case.  A lot of things are in log, but
they aren't related.

> > to the meaning, or why even bother adding it...especially considering
> > dynamic means "characterized by continuous change".  That hardly seems
>
> Well, at least we both have cute quotes now :).   I'm going to
> have to keep
> asking what's "continuously changing".

Well, if you understood the concept of dynamic range, then it would be
obvious ;-)

> > applicable to two static numbers!
> Aren't your maxpower and minpower measurements basically a
> "static" numbers.

Er, maxpower and minpower are YOUR numbers, not mine...

> What are you calling "continuous change"?   I don't see any "continuous
> change" when you measure the power amp and a certainly do see any
> continuous change when you get to the photo print.

If your measurements are 100 watts with a noise of 1 watt, then the amount
of change you can discern is 1 watt...any CHANGE must be 1 watt or greater
for you to perceive it.

> > > Dynamic range is a range just like any other range,  the word
> "dynamic"
> > > is just a qualifier that says "perceptually interesting part of".
> >
> > I don't mean to be snide, but that's just silly.  So many
> things have ranges
> > specified, and they aren't called "dynamic ranges",
> I didn't say all  ranges are dynamic.  I said a "dynamic range"
> is firstmost
> a range and it ought to AT LEAST have the notion of being a range.
> The "dynamic" is an ADDITIONAL modifier, qualifying additional limits.

I believe the intention of "dynamic range" is dynamics OF THE range.  I do
not know the history of the term, but perhaps that may be enlightening.

>    Well it seems that if we're defining DynRange of
> something whose key property is density, we ought to end of with some kind
> of range whose units are density.

Well, no.  Dynamic range is ALWAYS in dB, not density.  When you measure the
dynamic range of a audio equipment, you don't get volts, you bet dB.  That
is probably a MAIN source of your confusion.  dB IS dB, and is purely a
relative value, and has no unit BUT dB.

> Similarly you could be talking about the DynRange of a natural
> scene --  density wouldn't be to useful since there isn't any.

How's that?  Scenes absolutely have density.  If you can measure density on
a print, what's to say the print isn't the scene?

> Here
> you ought to use whatever units you can measure.  (My spotmeter does
> EV at ISO 100 for instance, so I'd be thinking of DynRange in EV's).

If you measure the dynamic range of your EV meter, say it has an overall
range of 20 EV, and is good to .1 EV, then it's dynamic range is
10log10(20/.1) or 23dB, NOT 23EV.

EVERY dynamic range equation shown has the result in dB.

Regards,

Austin

Hi Austin (is anybody else still listening?)

This discussion has gotten badly out of hand.  We seem to
be on totally different wavelengths of thought.  It certainly
hasn't been all bad, though.  No doubt, I've learned a few things
and its stimulated my thinking on the whole matter.

But:
We just barely agree what DynRange of audio is.  I'm not really sure!
We don't agree on DynRange of Imaging. (DROI)
We don't agree on whether DROI is one specify thing.
We don't agree on DROI has been used in the past.
We don't agree on DROI if used really is a misuse.
We don't agree on DROI changed from correct use to misuse
   because of the internet.
We don't agree on if there is a common use of DROI.
We don't agree on whether common use of DROI is a misuse.
etc. etc.

The dialogue seems to be bogging down in such esoteric and semantic
details that we can't see the forest from the trees.

I don't have the long history of working with the DynRange
concept you have.  But ... I've got a good math and science
background.  I have a pretty idea of the audio/hearing and
image/sight perception issues.  I'm not a super expert guru
in all this stuff, but the math is well within my experience
and the perception issues are simple enough.  For whatever its
worth my approach has been to look and research the whole
picture without an emphasis from one specific direction.

So. The only thing that makes a lot of sense to me now is to
spell out my logic.  I really don't we're in the realm of
proofs one way or the other.  I think you've said several times
that you can take DynRange of any variable you like.  Right?
If we start with "dynamic range of an image", no variable is
stated so who's to be the dictator of what the variable is?  

What follows is basically by definition just my opinion.
I've made choices based on what I think is important and
just plain: how I see it.  The whole package goes together.
There are many choices but they all relate in some way.

---------------------------------------------

There's a lot written about DynRange of audio and sound.
Most of my approach is in moving the concept from the audio
realm to the imaging realm.  I'm very influenced by the
parallelism of the physical properties, of the perception, and of
the math involved.   The parallelism is so compelling that
I place very high importance to it.  Modelling in the
abstract is used extensively in scientific research.  Here
we actually have two physical systems that can share a 
model or even model each other.

First some of the physical properties.  Both sound and
light are wavelike phenomena.  Sound is a pressure wave
moving through the air, there is an energy associated with
it the amplitude of the waveform determines the energy.
Likewise, light is an electromagnetic wave which has
an energy as well.  In both cases some source generates
the respective waves and they propagate in space.
We have ears and eyes to detect these waveforms.  A key
aspect is that both senses perceive linearly increasing
intensity when the underlying waveform has an 
exponentially increasing energy level. Or mathemtically
speaking the perception intensity is proportional to
the log of the waveform energy. This parallelism between
energy of the two waveforms and the perception of the
two waveforms is so strong that I believe it only makes
sense to apply the mathematical constructs in a similarly
parallel fashion.

In the audio realm we have:
The decibel dB is used extensively as a measure of a power ratio.

db = 10*log10(power1/power2)
If there are two power levels they differ by this many dB
given the levels power1 and power2.

There is one special dB measurement called dynamic range.
It has the same formula structure but uses two specific
power levels: the maximum power and the minimum power.

DynRange (dB) = 10 * log10 (maxpower/minpower)

It is basically a measure of the largest power ratio that
the audio system can produce.   Power is just energy
per time unit, so a power ratio is identical to an
energy ratio ( the "per time" unit whatever it is cancels
out in the ratio).  So DynRange becomes a measure of the
energy ratio in the loud sound wave vs. the quieter sound
wave.

Since sound and light have the same energy vs perception
characteristics, it makes sense to define DynRange for
light to also be a measure of the energy ratio of two
extremes -- called bright and dark. "bright" is the
max light energy and dark is the min energy. How shall
we measure light energy and what units?  Since we are
only ever interested in the ratio of two light energies,
the unit whatever they are always cancel.  Similarly,
we don't have to measure absolute values anyway -- just
get the ratio of the energies.  Well in photography
we do this all the time.  A one stop difference in light
is just a 2x difference in light energy i.e. ratio = 2.

As a photographer light ratios measured in stops is
used all the time.  But how do you get the ratio given
the number of stops?  1 stop = 2, 2 stops = 4, 3 stops  = 8.
Ratio = 2^numstops

Putting this all back into the dB formula we have:

dB = 10 * log10 (ratio)
   = 10 * log10 (2^numstops)
   = 10 * log10(2) * numstops
   = 3dB * numstops

Not surprisingly, this is the same as audio 3db = double power.

Now back to the main subject, DynRange.  With an appropriate
choice or measurement of maxlight value and minlight value,
we simply have:
DynRange (dB) = 3dB * (number of stops between min and max)

dB certainly could be the unit we do all calculations,
however in the imaging realm we have several units that are
already very well used.  We talk about stops everywhere in
photography -- making a new unit that is just 3 * stops
isn't necessary at all.  It makes sense to me that the unit
we use in imaging is the one that we already have. With
the  multitude of technologies involved in imaging, we
actually  have another unit that is very similar and thats
the density unit -- this is just 0.3 * stops.   It looks
very much like dB and if it didn't already exist already.
Looking at these three units they are all dimensionless
numbers that are the log of an energy ratio.  For historical
reasons stops are log base 2 whereas the others are log
base 10, otherwise they are all equivalent units.  Since
different imaging technologies have long used certain units, 
it makes sense to use the appropriate unit.  The conversion
is very simple anyway.

This sounds almost trivially simple but the important issue
is the choice of maxlight value and minlight value.
Conceptually, you just pick the brightest value and the
darkest value -- but there's lots of room for tweaking
the idea -- like does the value need texture or detail or
go just beyond that or what.

At this point I'm just showing a derivation that produces
a reasonable concept with an intuitive understanding and a 
potential measuring method.  It has a basic meaning that
matches the usage of the term in several existing areas.
Ansel Adams' book The Negative uses the term dynamic
range which is very similar -- the useful Zones or stops
for the Zone system.  The term in also used quite a bit
in the scanner realm and in that context the specification
"dynamic range" is stated as the range of densities that the
scanner can handle.

-----------------------------

So that's my take on dynamic range for imaging.  In my opinion
its the most natural way to define the idea.  I don't
think there are any large leaps of faith. Also, others have
used a similar concept.  I'd have to admit that there are
lots of usages that are not really technically defined.
But they seem to just mean that good dynamic range 
translates to "looks good tonally".  I can't really see
this as contradictory.

I haven't defined precise ways to define the max and min because
I think various people might want different standards for 
that -- just as the audio dynamic range equation doesn't
specify the standard for max and min.

I'd be glad to clarify anything in this discussion.  Austin,
if you would like to put your whole story together into
one package it would be very helpful to see where you stand.
I imagine this grates against you a bit, but ... I can't help it.
The discussion, as before, lost most of the semblence of
what we wanted to define.  I'd like to say I'm open minded
about the whole thing, but all the above fits so well.

-------------------

Best regards,

Roy

Roy Harrington
roy@...
Black & White Photography Gallery
http://www.harrington.com

Hi Roy,

My point in the entire discussion is that density range and dynamic range
are NOT the same.

I do plan on writing this up at some point in time, when I have time.

Austin

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Hi Roy,
> 
> My point in the entire discussion is that density range and dynamic range
> are NOT the same.
> 
> I do plan on writing this up at some point in time, when I have time.
> 
> Austin

Please do write your take of the matter.  I am interested how it comes out.

Please also reread my statement, and realize that I have NOT purely
equated density range and dynamic range.   I believe there are aspects
of imaging that are not modeled well as density (i.e. real scenes)
and they have dynamic range, too.  My dynamic range always 
boils down to a light energy range.

Roy