Digital BW, The Print

Roy,

A good post and I concur, for what it is worth. I am sorry I dropped out of
the discussion but it did not seem to be leading anywhere constructive.

I favor the simple explanation when it will do and the classic view of the
dynamic range in photography as being the ratio of the useable/meaningful
max and min seems to me to suffice quite nicely.

The one thing that I will add is that in both the audio and the imagining
models there is no mention of discrete or finite numbers of volume levels or
brightness levels. The implied assumption is that any level in between can
be used or achieved. Even if theory suggest a finite number of levels
actually exists, this seems totally irrelevant due to the factor of human
perception. If we could clearly hear or see distinct level changes in the
signal we would simply reject the audio or the image as being of
unacceptable quality.

Thanks,
Martin

----- Original Message -----
From: "royvharrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Monday, April 08, 2002 10:30 PM
Subject: [Digital BW] Final(ish) Ranges about Imaging


>
> 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
>
>
>
>
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--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" <mwesley250@e...> wrote:
> Roy,
> 
> A good post and I concur, for what it is worth. I am sorry I dropped out of
> the discussion but it did not seem to be leading anywhere constructive.

Thanks, Martin.  
> 
> I favor the simple explanation when it will do and the classic view of the
> dynamic range in photography as being the ratio of the useable/meaningful
> max and min seems to me to suffice quite nicely.

Simplicity in concepts is so important that it must be emphasized over
and over.  It has to be simple in the math, simple in the physical phenomena,
and simple in the human perception.  There's a philosophy caller "Occam's Razor".
For anyone not familiar with it, this dates back centuries to the 1300's to
a philosopher, William of Occam.  If there's any philosophy that I'd call
universally applicable to life, this is the one.  Go to www.google.com and search for
occam's razor --  its truly worth reading for any level of person for any
walk of life.

> 
> The one thing that I will add is that in both the audio and the imagining
> models there is no mention of discrete or finite numbers of volume levels or
> brightness levels. The implied assumption is that any level in between can
> be used or achieved. Even if theory suggest a finite number of levels
> actually exists, this seems totally irrelevant due to the factor of human
> perception. If we could clearly hear or see distinct level changes in the
> signal we would simply reject the audio or the image as being of
> unacceptable quality.

Yes, the physical phenomena of both light and sound are analog i.e. completely
continuous.  Similarly the human perception of both is also completely
continuous.  There are bounds (max and min) but between those its
continuous.   Discrete levels of either sound or light are only introduced by
manmade devices -- usually digital processing.

> 
> Thanks,
> Martin
> 

I had one email question that is relevant and I think its worth addressing here.

What about noise?  Where did that go?

Let's look at the audio realm and how it relates to the DynRange formula.

DynRange = 10 * log10 (maximum signal power / minimum discernable signal power)

The word discernable is where the noise factor comes in.  In audio the idea
is that at the low power end, the signal has to be strong enough to be
detected ABOVE the noise level.  Signals that are below this level cannot be
perceived or measured and should NOT be considered as part of the DynRange.
Noise is THE main limiting factor for the lower bounds of "useful" signal.

So how does this relate to imaging?
First I think there is a semantics or language problem.  We use "noise" a whole lot
in sound:  everybody has had the experience of sitting is a "noisy"
restaurant or bar.  People can easily relate to the word and idea that in the noisy
bar, you have to shout for the other person to hear you (sound familar?, the signal
has to be greater that the noise in order to be discernable).

I've never heard anyone look at a scene in the real world and remark:  what is
see sure is noisy.  The word from an language point of view doesn't have an
obvious, customery usage in imaging.  But, of course we're all somewhat savvy
to technical terms and we have a feeling of what noise is.  I think about the
only way to talk about noise in light is from the point of view of something
detecting or measuring light levels.  In measuring a light level, if the image light
level is so low that extraneous light masks the image, then the image light
it down below the light noise and therefore undiscernable.

Lets try an example.  Scene of a white barn out in the sun, there's a door open
that goes way back to a distant wall.  There are no windows so the inside
is very dark.  Lets measure light using our eye and using a spotmeter.  From
the outside neither our eye nor the meter can get a "meaningful" reading.
We can go inside and both the eye and meter work perfectly, they are both
plenty sensitive: we can see and measure lots of different light levels
inside the barn.  Back outside again, we see a black hole: nothing whatsoever,
the meter comes up with a reading but its entirely governed by flare and
other extraneous info.  This is what I would call noise in the scene.  There are just
too many extraneous light levels to detect the real image light level.  For
the eye case I'm sure there are light waves hitting the retina is the area
corresponding to the dark door.  But the brain is well aware that the noise
in that area is dominating and so doesn't bother us with a useless perception.

This idea of noise is what I think is relevant to Dynamic Range.   Its just
a matter of image signal must be greater than the extraneous light
energy for the image signal to be "useful"  and therefore within the DynRange.
This concept is pretty easy to see in real scenes but when talking about
image prints most of this isn't very relevant.  A print on paper is an abstraction
of a real world scene.  The real world scene can potentially extend without
bounds towards dark and towards light.  There's no inherent limit to the
max or min energy in the light waves.  On a print the paper has absolute
limits the white of the paper and the black of the most black stuff we can
put on the paper.  In an appropriate light, we can easily see or detect all light
levels that could possibly be emitted.  So the issue of noise (extraneous
light) limiting the max or min light level from a print just doesn't exist at all.
(Aside: viewing a print under glass in a glary area would be an example
of an "inappropriate" light that would probably limit our seeing max to min).

Before there's a bunch of objections, I think there is also a very different
phenomena that a lot of people might think of as noise in imaging.  Many
imaging technologies represent light values in discrete chunks.  Film is all
based of grains of silver, prints are grains or for inkjet they are dithered
dot patterns.   They are all based on representing continuous light data
as many little pieces that all averaged together to make our perception
appear continuous.  The technologies all use various different "chunk"
sizes: some are large like fast film or like a printer with big ink drops;
others are small like slow fine grain film or the newest high dpi printer.
I think we refer to this "chunkiness" as noise as well.  The noisiness is
function of how much stuff we perceptually have to average over to make
our perception appear continuous.  If averaging is too small an area we see the
chunkiness and call it noisy, if the averaging area is larger the chunkiness
goes away and its less noisy.   Note that this phenomena is just in the
imaging technologies, there's nothing is real scenes that corresponds
to this.   This kind of noise is certainly has has a long history in imaging
and is important as a concept in imaging, but I don't think it plays any role
in the Dynamic Range concept.

Here's an illustration:  Imagine a print made from a very grainy piece of
film.  The print spans the whole paper range -- bright white area to
deep deep blacks -- and of course there's lots of grays in between.
Look at the print from close up.  There's lots of grain, lots of chunkiness,
and lots of noise.  Now back up, our eyes now have to average light
info over a larger area due to limited eye resolution.   Its exactly the
same print but the grain, the chunkiness, and the noise all start to
disappear.  Soon there is just completely continuous perception. 
The max white and max black are still the same light levels.
Has the dynamic range of the print mysteriously changed?  Shall we
talk about a PROPERTY OF THE PRINT which changes even though
its the same print, same light, same eyes?   I say probably not.

Thanks for reading.
-Roy

I posted this a while ago, and it seems yahoo lost it.
If it turns out as a duplicate, sorry.  --Roy

--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" <mwesley250@e...> wrote:
> Roy,
> 
> A good post and I concur, for what it is worth. I am sorry I dropped out of
> the discussion but it did not seem to be leading anywhere constructive.

Thanks, Martin.  
> 
> I favor the simple explanation when it will do and the classic view of the
> dynamic range in photography as being the ratio of the useable/meaningful
> max and min seems to me to suffice quite nicely.

Simplicity in concepts is so important that it must be emphasized over
and over.  It has to be simple in the math, simple in the physical phenomena,
and simple in the human perception.  There's a philosophy caller "Occam's Razor".
For anyone not familiar with it, this dates back centuries to the 1300's to
a philosopher, William of Occam.  If there's any philosophy that I'd call
universally applicable to life, this is the one.  Go to www.google.com and search for
occam's razor --  its truly worth reading for any level of person for any
walk of life.

> 
> The one thing that I will add is that in both the audio and the imagining
> models there is no mention of discrete or finite numbers of volume levels or
> brightness levels. The implied assumption is that any level in between can
> be used or achieved. Even if theory suggest a finite number of levels
> actually exists, this seems totally irrelevant due to the factor of human
> perception. If we could clearly hear or see distinct level changes in the
> signal we would simply reject the audio or the image as being of
> unacceptable quality.

Yes, the physical phenomena of both light and sound are analog i.e. completely
continuous.  Similarly the human perception of both is also completely
continuous.  There are bounds (max and min) but between those its
continuous.   Discrete levels of either sound or light are only introduced by
manmade devices -- usually digital processing.

> 
> Thanks,
> Martin
> 

I had one email question that is relevant and I think its worth addressing here.

What about noise?  Where did that go?

Let's look at the audio realm and how it relates to the DynRange formula.

DynRange = 10 * log10 (maximum signal power / minimum discernable signal power)

The word discernable is where the noise factor comes in.  In audio the idea
is that at the low power end, the signal has to be strong enough to be
detected ABOVE the noise level.  Signals that are below this level cannot be
perceived or measured and should NOT be considered as part of the DynRange.
Noise is THE main limiting factor for the lower bounds of "useful" signal.

So how does this relate to imaging?
First I think there is a semantics or language problem.  We use "noise" a whole lot
in sound:  everybody has had the experience of sitting is a "noisy"
restaurant or bar.  People can easily relate to the word and idea that in the noisy
bar, you have to shout for the other person to hear you (sound familar?, the signal
has to be greater that the noise in order to be discernable).

I've never heard anyone look at a scene in the real world and remark:  what is
see sure is noisy.  The word from an language point of view doesn't have an
obvious, customery usage in imaging.  But, of course we're all somewhat savvy
to technical terms and we have a feeling of what noise is.  I think about the
only way to talk about noise in light is from the point of view of something
detecting or measuring light levels.  In measuring a light level, if the image light
level is so low that extraneous light masks the image, then the image light
it down below the light noise and therefore undiscernable.

Lets try an example.  Scene of a white barn out in the sun, there's a door open
that goes way back to a distant wall.  There are no windows so the inside
is very dark.  Lets measure light using our eye and using a spotmeter.  From
the outside neither our eye nor the meter can get a "meaningful" reading.
We can go inside and both the eye and meter work perfectly, they are both
plenty sensitive: we can see and measure lots of different light levels
inside the barn.  Back outside again, we see a black hole: nothing whatsoever,
the meter comes up with a reading but its entirely governed by flare and
other extraneous info.  This is what I would call noise in the scene.  There are just
too many extraneous light levels to detect the real image light level.  For
the eye case I'm sure there are light waves hitting the retina is the area
corresponding to the dark door.  But the brain is well aware that the noise
in that area is dominating and so doesn't bother us with a useless perception.

This idea of noise is what I think is relevant to Dynamic Range.   Its just
a matter of image signal must be greater than the extraneous light
energy for the image signal to be "useful"  and therefore within the DynRange.
This concept is pretty easy to see in real scenes but when talking about
image prints most of this isn't very relevant.  A print on paper is an abstraction
of a real world scene.  The real world scene can potentially extend without
bounds towards dark and towards light.  There's no inherent limit to the
max or min energy in the light waves.  On a print the paper has absolute
limits the white of the paper and the black of the most black stuff we can
put on the paper.  In an appropriate light, we can easily see or detect all light
levels that could possibly be emitted.  So the issue of noise (extraneous
light) limiting the max or min light level from a print just doesn't exist at all.
(Aside: viewing a print under glass in a glary area would be an example
of an "inappropriate" light that would probably limit our seeing max to min).

Before there's a bunch of objections, I think there is also a very different
phenomena that a lot of people might think of as noise in imaging.  Many
imaging technologies represent light values in discrete chunks.  Film is all
based of grains of silver, prints are grains or for inkjet they are dithered
dot patterns.   They are all based on representing continuous light data
as many little pieces that all averaged together to make our perception
appear continuous.  The technologies all use various different "chunk"
sizes: some are large like fast film or like a printer with big ink drops;
others are small like slow fine grain film or the newest high dpi printer.
I think we refer to this "chunkiness" as noise as well.  The noisiness is
function of how much stuff we perceptually have to average over to make
our perception appear continuous.  If averaging is too small an area we see the
chunkiness and call it noisy, if the averaging area is larger the chunkiness
goes away and its less noisy.   Note that this phenomena is just in the
imaging technologies, there's nothing is real scenes that corresponds
to this.   This kind of noise is certainly has has a long history in imaging
and is important as a concept in imaging, but I don't think it plays any role
in the Dynamic Range concept.

Here's an illustration:  Imagine a print made from a very grainy piece of
film.  The print spans the whole paper range -- bright white area to
deep deep blacks -- and of course there's lots of grays in between.
Look at the print from close up.  There's lots of grain, lots of chunkiness,
and lots of noise.  Now back up, our eyes now have to average light
info over a larger area due to limited eye resolution.   Its exactly the
same print but the grain, the chunkiness, and the noise all start to
disappear.  Soon there is just completely continuous perception. 
The max white and max black are still the same light levels.
Has the dynamic range of the print mysteriously changed?  Shall we
talk about a PROPERTY OF THE PRINT which changes even though
its the same print, same light, same eyes?   I say probably not.

Thanks for reading.
-Roy

Roy,

> Simplicity in concepts is so important that it must be emphasized over
> and over.

Absolutely, but too simple, and the concept can be lost.

> Similarly the human perception of both is also completely
> continuous.

This is the concept you seem to not be understanding.  You can have two
sounds/tones that ARE completely different (as determinable by SOME sensing
device), but YOU perceive them (or some sensory device) exactly the same,
indistinguishable from each other...no matter how hard you try.  That IS the
concept of dynamic range plain and simple.  It is NOT the OVERALL range, but
describes what the PERCEPTIBILITY is within that overall range.  Simple as
that.  It's relative within the range (in the analog case), NOT absolute.
In the digital case, it is absolute.

VERY simple example.  You have one sensory system that can perceive a 1/10th
range difference.  Another that, using the EXACT same range, can perceive a
1/100th range difference.  The one that perceives a 1/100th range difference
has a higher dynamic range.

EVERY sensing device has it's own dynamic range in and of it self.  Film is
a sensing "device".  When you are using a sensing device to sense
"information" from another sensing device, like film and a film scanner.
The dynamic range of the scanner is entirely separate from the dynamic range
of the film.  That also leads to why density range has nothing to do with
dynamic range...as both can "sense" the same density range, let's say, but
their dynamic ranges are entirely different.

Austin

Austin,

I really don't want to argue these little snipets of what DyR should be
or shouldn't be.  I think its going to be necessary for you to lay the
whole thing out so we can all see the sum total of your ideas.  There's
a lot of confusion with me and I suspect others understanding some of
your points.  When stating my stuff, I tried to put in a bunch of examples
to illustrate what I was saying.  I hope you feel inclined to do the same.
I think its particularly useful if the examples are related to how we
humans perceive light and/or sound.  DynRanges of digital volt meters
or whatnot may be useful to you but don't help the rest of us "get it".

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Roy,
> 
> > Simplicity in concepts is so important that it must be emphasized over
> > and over.
> 
> Absolutely, but too simple, and the concept can be lost.
> 
> > Similarly the human perception of both is also completely
> > continuous.
> 
> This is the concept you seem to not be understanding.  You can have two
> sounds/tones that ARE completely different (as determinable by SOME sensing
> device), but YOU perceive them (or some sensory device) exactly the same,
> indistinguishable from each other...no matter how hard you try.  
Sorry to sound snide, but "So What?".

That IS the
> concept of dynamic range plain and simple.  
If this is DyR and its unperceivable, then "So What?".

It is NOT the OVERALL range, but
> describes what the PERCEPTIBILITY is within that overall range.  Simple as
> that.  It's relative within the range (in the analog case), NOT absolute.
> In the digital case, it is absolute.
> 
> VERY simple example.  You have one sensory system that can perceive a 1/10th
> range difference.  Another that, using the EXACT same range, can perceive a
> 1/100th range difference.  The one that perceives a 1/100th range difference
> has a higher dynamic range.

Sounds more like higher sensitivity.

> 
> EVERY sensing device has it's own dynamic range in and of it self.  Film is
> a sensing "device".  When you are using a sensing device to sense
> "information" from another sensing device, like film and a film scanner.
> The dynamic range of the scanner is entirely separate from the dynamic range
> of the film.  That also leads to why density range has nothing to do with
> dynamic range...as both can "sense" the same density range, let's say, but
> their dynamic ranges are entirely different.
> 
> Austin

So, let me paraphrase what I think you are saying with an example.  I like
to use the audio world because MAYBE we are more likely to agree.

Say I'm a audio power amp manufacturer.  I make amps, test them however
you'd like.  I put a spec in the manual stating "Dynamic Range 64db".
Is that a reasonable thing to do?   Is 64dB a property of the amp?

Now one of my suppliers comes along and says he's really improved the
test equipment.  It can perceive a range difference 10 times more accurately.
Now we can perceive i.e. measure differences in the amplifier much
more accurately.

You say and I quote from above: Dynamic Range " is NOT the OVERALL range, but
> describes what the PERCEPTIBILITY is within that overall range."
So I ask you:  Did the amplifiers just get better?  Is the dynamic range
of the amplifier now 74db  =  (64db + 10*log10(10)).  Do I have to 
reprint all the specs?

Please explain.

Roy

If you'll read the brief article at this webpage carefully, you'll 
see that it's in agreement with what Austin has been saying.

http://www.library.cornell.edu/preservation/tutorial/intro/intro-
05.html


The two pictures of the buildings are a perfect illustration of 
images with identical "density range" (i.e., they both go from full 
white to full black), but with different "dynamic ranges".

Also, don't be fooled (as I was, at first) by the phrase, "the 
dynamic range does not automatically correlate to the number of tones 
reproduced".  That phrase isn't saying that Austin's understanding 
of "dynamic range" is wrong.  It's saying that Austin' understanding 
is right, but that an image system's dynamic range is merely 
potential, and that it may still produce images that don't make full 
use of its dynamic range.  -- Herb

Roy,

> I think its particularly useful if the examples are related to how we
> humans perceive light and/or sound.

But that has nothing to do with dynamic range being dynamic range.  That
only has to do with OUR perception.  We are NOT the film, we are NOT the
film scanner, and the perception of film and scanner are VERY important in
producing the image that WE see...it takes more than just what WE perceive
when we look at the final print.

> DynRanges of digital volt meters
> or whatnot may be useful to you but don't help the rest of us "get it".

Dynamic range of both film and scanners IS useful, and I've illustrated
those.

> > > Similarly the human perception of both is also completely
> > > continuous.
> >
> > This is the concept you seem to not be understanding.  You can have two
> > sounds/tones that ARE completely different (as determinable by
> SOME sensing
> > device), but YOU perceive them (or some sensory device) exactly
> the same,
> > indistinguishable from each other...no matter how hard you try.
>
> Sorry to sound snide, but "So What?".

Sigh.  That's the root of our disagreement.  You don't get the significance
of this, and how it relates to dynamic range, and that's why you don't
understand my use of dynamic range, and also why dynamic range (as I've used
it) is important as a specification/interest/property.

> > That IS the
> > concept of dynamic range plain and simple.

> If this is DyR and its unperceivable, then "So What?".

I DID NOT say it's unperceivable at all!  It is the "limit of
perceivibility" (over a specified range), say in a sensor systems (like your
eyes).

> It is NOT the OVERALL range, but
> > describes what the PERCEPTIBILITY is within that overall range.
>  Simple as
> > that.  It's relative within the range (in the analog case), NOT
> absolute.
> > In the digital case, it is absolute.
> >
> > VERY simple example.  You have one sensory system that can
> perceive a 1/10th
> > range difference.  Another that, using the EXACT same range,
> can perceive a
> > 1/100th range difference.  The one that perceives a 1/100th
> range difference
> > has a higher dynamic range.
>
> Sounds more like higher sensitivity.

ER, yeah.  BUT sensitivity is not based on the overall range, as dynamic
range is.

Sensitivity doesn't give you any ability to compare different
"systems"...but dynamic range does.  You could have a system that has a huge
range, but really low sensitivity...and a system that has a smaller range,
but very high sensitivity (just like positive film vs negative film as one
example ;-)...and neither the range, or the sensitivity (by them selves)
mean anything when trying to compare the two, but the dynamic range, as I
have used it, does give you a meaningful comparison.

<snip>

> Do I have to
> reprint all the specs?

Providing your measuring equipment was "better" than the noise in the amp,
no.

You give me "so what"'s for things that are very important, and you just
dismiss them!  I am sorry to say, but I really feel like I'm wasting my time
if you're not going to try to understand why those things are important.

One thing that would be interesting (at least to me), and since you seem to
have a lot of time for research ;-) would be to find out the origin of the
term "dynamic range", and what it meant to the person/people who first used
it.

Austin

Herb,

I posted that link and definition along with some others for Austin awhile
back and he dismissed it as pedestrian, vague and unscientific since it did
not include an equation and a precise definition of "lightest light and
darkest dark ".

Austin has consistently said that photographs are not continuous tone and
that the knowing the dynamic range tells you how may tones there are. Austin
has specifically said that something like microfilm has a much lower dynamic
range because it has fewer tones than conventional B&W film.

This definition is a pretty good one by the way. But what they show in their
examples is more often thought of as contrast differences rather than
dynamic range differences.

Martin

----- Original Message -----
From: "hsitz" <hsitz@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Tuesday, April 09, 2002 7:29 PM
Subject: Re: [Digital BW] Final(ish) Ranges about Imaging


> If you'll read the brief article at this webpage carefully, you'll
> see that it's in agreement with what Austin has been saying.
>
> http://www.library.cornell.edu/preservation/tutorial/intro/intro-
> 05.html
>
>
> The two pictures of the buildings are a perfect illustration of
> images with identical "density range" (i.e., they both go from full
> white to full black), but with different "dynamic ranges".
>
> Also, don't be fooled (as I was, at first) by the phrase, "the
> dynamic range does not automatically correlate to the number of tones
> reproduced".  That phrase isn't saying that Austin's understanding
> of "dynamic range" is wrong.  It's saying that Austin' understanding
> is right, but that an image system's dynamic range is merely
> potential, and that it may still produce images that don't make full
> use of its dynamic range.  -- Herb
>
>
>
> 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
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> - 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/
>
>
>

> If you'll read the brief article at this webpage carefully, you'll
> see that it's in agreement with what Austin has been saying.
>
> http://www.library.cornell.edu/preservation/tutorial/intro/intro-
> 05.html
>
>
> The two pictures of the buildings are a perfect illustration of
> images with identical "density range" (i.e., they both go from full
> white to full black), but with different "dynamic ranges".
>
> Also, don't be fooled (as I was, at first) by the phrase, "the
> dynamic range does not automatically correlate to the number of tones
> reproduced".  That phrase isn't saying that Austin's understanding
> of "dynamic range" is wrong.  It's saying that Austin' understanding
> is right, but that an image system's dynamic range is merely
> potential, and that it may still produce images that don't make full
> use of its dynamic range.  -- Herb


Thanks, Herb...I believe that article can actually go both ways!  This is
the root of the confusion about what dynamic range really is...it's just so
easy to have it explained to you, and think you get it, but don't.

Only one sentence on that page "bothers" me:

"For instance, high-contrast microfilm exhibits a broad dynamic range, but
renders few tones"

If they said "broad DENSITY range" it would have better matched my
understanding...because I believe high contrast microfilm exhibits a low
dynamic range, but does in fact have a high density range.

I can find dozens of web sites that the understanding can go either
way...which means Roy (and others who believe as he does) can cite a lot of
"supporting" information, and I can do the same from dozens of other web
sites... Sigh.  The web is clearly not the answer...

Regards,

Austin

Austin -- You're not making enough of it. ;)

At the very least, that article is helpful to your understanding 
because it seems to distinguish two different senses of dynamic 
range.  One that has to do merely with the difference between darkest 
and lightest shades, and one that has to do with the number of tones 
that can be rendered between those two endpoints. Most of the people 
disputing your understanding in the various threads have maintained 
that dynamic range has nothing to do with the number of tones 
representable, just with the difference between highest and lowest.  
This article demonstrates at the very least that using "dynamic 
range" to refer to the number of representable (or represented) tones 
is an appropriate use of the term.  

Moreover, the article emphasizes the importance of 'dynamic range' 
when understood as having to do with the number of representable 
tones:

 "Dynamic range also describes a digital
  system's ability to reproduce tonal information.
  This capability is most important for 
  continuous-tone documents that exhibit 
  smoothly varying tones, and for photographs
  it may be the single most important 
  aspect of image quality."

Finally, the example pictures clearly favor your understanding, 
because the difference between the high dynamic range pictures and 
the low dynamic range pictures has to do only with the number of 
tones represented, not with the highest and lowest tonal values; all 
pictures appear to vary from full white to full black, and so to have 
equal dynamic range using that term as most of the people disagreeing 
with you have used it.  

-- Herb

--- In DigitalBlackandWhiteThePrint@y..., "hsitz" <hsitz@n...> wrote:
> If you'll read the brief article at this webpage carefully, you'll 
> see that it's in agreement with what Austin has been saying.
> 
> http://www.library.cornell.edu/preservation/tutorial/intro/intro-
> 05.html
> 
> 
> The two pictures of the buildings are a perfect illustration of 
> images with identical "density range" (i.e., they both go from full 
> white to full black), but with different "dynamic ranges".
> 
> Also, don't be fooled (as I was, at first) by the phrase, "the 
> dynamic range does not automatically correlate to the number of tones 
> reproduced".  That phrase isn't saying that Austin's understanding 
> of "dynamic range" is wrong.  It's saying that Austin' understanding 
> is right, but that an image system's dynamic range is merely 
> potential, and that it may still produce images that don't make full 
> use of its dynamic range.  -- Herb

Hi Herb,

I'd seen that page before.   I think you're going to have a hard time
proving much one way or the other with this description.

Like you said both images go from black to white, but you are also looking
at both images on your monitor, right.  Your monitor displays up to 256
levels of gray.  Maybe you can't distinguish them all but whatever ones
you can distinguish are going to be the same for both pictures.  I.e.
counting number of grays in the two pictures is going to be almost 
entirely dependent on your monitor.

For anyone who has done a lot of darkroom printing, there'a an immediate
response to those two pictures.  The bum one is printed too contrasty.
Its done with the wrong grade paper.  The description of what's wrong
with it, is right there -- the lack of detail in shadows and highlights.
This is exactly too contrasty.

They talk about "limited dynamic range".  What do they mean?  I think
the way they are using the term is often found.   I don't they are
really talking about the grays in the final print (or jpg).  I think they
are interested in whether the distinguishable grays in the original
scene show up as distinguishable grays in the final print.  The problem
is the distinguishable grays in the shadows of the original scene show
up as way too dark in the print.   My translation is that the
dynamic range of the original scene (we would have seen shadows and
highlights) is poorly represented in the dynamic range of the final
print.  In other words the lower end (the dark parts) of the print come
from a much higher (brighter) portion of the dynrange of the original
scene.  The part of the original dynrange going from the bottom to
the brighter parts (referenced immediately above) is unfortunately
bunched all together into the very darks in the print i.e. no shadow
detail.  Or final translation: A limited portion of the dynamic range
of the original scene is show in the dynamic range of the final print.

Hopefully I said that clear enough, a picture would be so nice!
Semantics is tricky here, but people use terms without being
very precise sometimes.

Roy

I am sorry to say, but I really feel like I'm wasting my time
> if you're not going to try to understand why those things are important.
> 

> Austin

Well, Austin, I think I understand a lot more about what you are saying
than you want to understand about what I am saying.  You seem
to be so sure of your position that you don't want to "hear"
any other ideas.  You've worked for years using the dynamic range
concept in a totally different context, and feel that that experience
makes you perfectly suited to define it in a totally new context.  
On the surface that sounds like a reasonable conclusion.  And
because of that I spent some time researching the concept
and listening to your ideas.   But, after careful consideration I've
decided that I disagree with several claims you've made about
dynamic range as it relates to our specific context.

Its not that I don't understand, its that I don't agree.   I've tried
to figure out why we both can agree and start from a very
simple looking dynamic range formula and come out with different
views.  I'm just guessing but I still think the discrepancy arises
from the difference in linear scales versus exponential scales
when applied to the DynRange equation.  I mentioned this before
but I think you dismissed that as irrelevant.  If I can't get you to
think about that, how can I possibly discuss it?
--- In simplest form: I think most of your Dyr claims are based
on the underlying scale being linear.  I think the two perceptual
contexts we have, sound and light, are exponential and therefore
DyR has different properties.  But you'll have to at least consider 
this possibility before we're going to make progress.

Roy

--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" 
<mwesley250@e...> wrote:
> Herb,
. . .
> This definition is a pretty good one by the way. But what they show 
in their
> examples is more often thought of as contrast differences rather 
than
> dynamic range differences.
> 
> Martin

Martin -- Doesn't that make you think you might be missing 
something?  I mean, you claim to think the page is offering a pretty 
good definition of dynamic range, and then you claim that the 
pictures they've put there to illustrate precisely that concept "are 
more often thought of" as illustrating something different than the 
precise concept they're purporting to illustrate!!!  If it were me, 
I'd start to wonder about the discrepancy.

I'm sorry, and I guess we'll all have to agree to disagree, but I'm 
confident that Austin's definition of dynamic range is the correct 
one.  Of course, that doesn't mean that in more casual use (and maybe 
sometimes even in less casual use) that dynamic range may not be used 
to refer to density range.  And really, the dispute doesn't matter, 
so long as we're careful to distinguish what we're talking about.  
I.e., we should clarify whether we're talking about the difference 
between darkest dark and lightest light, or about the subtleness of 
transitions between different tones.  That's really all that's 
necessary.

By the way, I don't think the reference to "continuous tone 
documents" has anything to do with analog processes being infinitely 
variable.  A continous tone document can be printed by either analog 
or digital processes.  A continuous tone printer is merely one that 
puts down solid colors, not merely making use of dithering different 
colors to give the impression of a single solid color.  Inkjet 
printers are not truly "continous tone", which means merely that they 
dither other colors to create single solid colors (in their case they 
dither cyan, magenta, and yellow, and black).  But the size of the 
dots in inkjets has gotten so small that for any practical purpose 
they can be considered "continous tone" printers.  Some digital 
printers are truly "continous tone", though, like those that use dye 
sublimation technology.  -- Herb

Austin,

I sense you don't have the time to continue this thread to a conclusion now,
so without further response from you this will be my last post, at least to
you, on this topic. But I post this as a summary of where I stand. I believe
these are some of the issues your report will need to address to be
persuasive to a larger audience.

There have been three overlapping issues at play in this discussion.

A) What does the term Dynamic range refer to, and how is it distinct from
any other range.

B) How is DyR ascertained, and to what components is it applicable?

C) Why, in continuous tone photography, is the term DyR used so broadly
differently than what you established in A? There are pedestrian audiophiles
too, but the usage has remained steady in that field.

I think you've done a nice job with A, kudos, it wasn't easy; but B and C
are still lacking. I will try to address them separately below, but it
rambles, and there is a lot of overlap.

--------

How is DyR ascertained, and to what components is it applicable?


I believe your efforts so far have been more keenly geared toward a
discussion of the DyR of a print as the output of a "system". I've been
looking at that, but also at the print as an "object", where the system may
be unknown.

If you decide that DyR is more a measure of a system than an object then I
think we may have the basis for agreement. When I say "system:" I mean a
process where you feed known input values then measure/observe how well
(probably how linearly (within whatever scale you are working in, Roy))
those values get mapped upon output.

I think the notion that DyR applies more to a system than an object is not
far fetched. An audio system has a DyR, but you can't determine the DyR of a
loudspeaker without knowing what values are being fed to it, can you? I'd
think not, because you don't know if the sound you measure coming out
contains the loudspeaker's own noise or a faithful rendering of noisy input
values. You also don't know if the max and min are its limitation, or the
input value's. And so it goes for a print when viewed apart from a system.

As a side issue, if you had said that the Piezo system allows for better
tonal separation or delineation within its range than silver, there may
never have been an argument. But you said Piezo prints have better DyR than
silver, and that DyR means number of tones. But with Piezo's LOWER density
range, and on the matte papers we usually use, HIGHER noise than the more
common smooth surfaced silver papers, it is off to a poor start in the DyR
equation, relative to silver. THAT is what makes the DyR issue complicated.
With less DnR, and more noise, where is it's (purported) superior DyR
from??? This is critical and you have yet to address it.
 
As I've maintained, I believe the key to your logic lies in Piezo's better
linearity* (which is not true of all digital workflows), but the DyR
equation [(max-min)/noise] does not even address linearity. You were very
critical to those who were loose with the terms "max" and "min", but I feel
you have been equally loose with "noise". Noise seems to be a big catchall
phrase which seems to imply, "where the system fails", or "where linearity
is not maintained". I will address noise again in the next section.

(* By linearity I mean input values may get compressed or expanded to fit
into the next generation's range, but they do so in a uniform fashion, with
no more compression/expansion to one part of the range than another.)

---------

Why in continuous tone photography is the term DyR so broadly used
differently than what you established in A? There are pedestrian audiophiles
too, but the usage has remained steady in that field.


It comes full circle to where this began with Martin. He questioned if you
did take the DyR approach as you know it, which was probably born in the
field of electronics, and apply it to a chemical based process like a print,
would the concepts still apply; and to which I added: should the approach be
the same? Or, is the "noise" insignificant, such that you can just drop it,
or perhaps consider it numerically as one, which would I guess imply
linearity, and consider RANGE as dynamic range, and presume stepless tones -
at least from the standpoint of human perception - are available within that
range? 

You've asked, what then is dynamic about that range? What makes the range
dynamic is its degree of malleability. That's why conventional silver papers
have a greater DyR than a material like litho. Silver's range can vary
substantially based on exposure and development. Litho materials have very
strict thresholds with very little flexibility. However you handle litho
material you get the same range, not so conventional materials.

Here's an analogy. Looking at a rubber band, what is relevant, its range, or
the number of intermediary positions within that range? I think range. Even
if you could count its intermediary positions, why would you, when
continuity can be assumed?

Rubber bands, like silver prints, have a high DyR, while twine, like litho,
has low DyR. Now in your DyR equation, what distinguishes DyR from density
range? Noise.

But in looking at the rubber band vs twine, what distinguishes their dynamic
range? The malleability of their range - certainly not noise. See, the DyR
equation doesn't uphold the concept here. And if it seems silly to be
thinking of the DyR and noise of rubber bands and twine, so might it be for
prints. 

Now there is one ambiguity in all that, which relates to "B" above. I said
range may be all that need be considered in a print, but clearly a
conventional print (by virtue of it's malleability) is *capable* of far more
tones than a litho print (if there is such a thing as litho paper), in spite
of the fact that they may share the same density range. Do I wish to ignore
that fact?

No, but unutilized capability is irrelevant to an object. It's like saying a
circle isn't a circle because it could have been a square.

Take a litho neg and make an enlargement of it onto two papers: 1)
conventional silver paper, and 2) a litho paper - such that the prints have
the same DnR. In this instance the prints, as objects, will have the same
DnR AND DyR. They have to, they will be essentially the same print,
regardless of whatever unutilized capability either may have.

This speaks to the difference between a system, which has capability, and an
object, which just is. A print is an object. A print as object, like a
rubber band, just might need only be defined by its range.

If one *were* ambitious enough to try to count a rubber band's intermediary
positions (tones) should they use the DyR [(max-min)/noise] formula, or
would something else be required? First I'd wonder what would constitute
noise in a rubber band such that it would force intermediary stops?

Finally, isn't it true that a rubber band, when it's NOT being pulled or
pushed (a state of rest which I use to represents a finished print as
object), is its range still dynamic, or does it just have a length (range)?

----------

Where I think Roy, Martin, and myself are in agreement is that this
conversation will be greatly served when you clearly define just what it is
you maintain, even if you are not yet able to "prove" it. I think we all may
be more in agreement than it would appear, but that depends upon you. ;-)

Todd

PS, I good luck with your projects and peace to your family. I'm happy for
you you have more important things on your plate. But remember, you started
this. :-)

> Austin,
> 
> I sense you don't have the time to continue this thread to a 
> conclusion now,

Todd, it appears as if it would be a life long endeavor!

;-)

>> Austin,
>> 
>> I sense you don't have the time to continue this thread to a
>> conclusion now,
> 
> Todd, it appears as if it would be a life long endeavor!
> 
> ;-)

Just say Uncle... ;-)

Todd

> >> Austin,
> >> 
> >> I sense you don't have the time to continue this thread to a
> >> conclusion now,
> > 
> > Todd, it appears as if it would be a life long endeavor!
> > 
> > ;-)
> 
> Just say Uncle... ;-)

Fat chance!

Austin

>>>> Austin,
>>>> 
>>>> I sense you don't have the time to continue this thread to a
>>>> conclusion now,
>>> 
>>> Todd, it appears as if it would be a life long endeavor!
>>> 
>>> ;-)
>> 
>> Just say Uncle... ;-)
> 
> Fat chance!

Better get started soon then, I might not live as long as you. Anyway, don't
invest too much time in it, whatever you come up with I'm sure one of us
will destroy it overnight. ;-)

Todd