Digital BW, The Print

Hi Austin,

Wow!  There's definitely two different brain wave lengths in progress.
But, seriously, I've spent a fair amount of time understanding your position
on the whole matter.  I've seen your long discussions with others in this thread
and awhile ago on the Piezo list.  My gut feel was against some of your claims
but gut feel certainly isn't much of an argument (is it:) ).  So I didn't jump in
right away.  I figured out what you were saying and thought a lot about what
"made sense" to me.  I understand and acknowledge the concepts and
formulas you've used and derived.  You've contributed a lot to this group and
probably have a fair amount of influence.  Heck, you are persistant:)  

Anyway, I'm hoping I can convince you to try and understand my position
as opposed to re-explaining what you are doing.  I'm sorry that I have an unfair
advantage since I'm been reading your stuff much longer than you've seen mine.
You've got "over 25 years" of experience in dynamic range related stuff.  This is
great but I'm assuming most if not all is in the audio/video world.  I'm not usually
a name dropper but I do have two EE degrees from MIT and Stanford so I'm
not a techno-neophyte.  

I sure you have a very good intuitive and technical feel for audio and similar
systems.  I'll only claim pretty good for me.  While concept of dynamic range of
prints has been around, I think the technical definition and calculation of dynamic
range of prints is relatively new.

The way humans perceive sound versus a print is very different.  How you map
concepts in one to the other is not all trivial and predefined.


--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <darkroom@i...> wrote:
> Hi Roy,
> 
> > The real issue here is the "leap" of interpretation.  Let's go
> > back to the Higgins
> > book -- to the pages about dynamic range.  There's the formula on one page
> > (using the word signal) and there's the sine wave diagram on the next page
> > (the same one you posted way back).
> 
> The diagram that I posted a picture of, was actually NOT a sine wave (there
> is a sine wave to the left of it on the page, but that's not what I posted),
> but a picture of a grove in an analog record ;-)

Sorry, I was going from memory.  But the gist is exactly the same: when you
put the record on a player the moving needle creates a voltage that mimics
the same shape.

> 
> > The sine wave diagram talks about
> > "signal" and shows a large amplitude and a small amplitude.  In
> > the audio world
> > its real easy to look at it and think "voltage" oscillating back
> > and forth over time.
> 
> Hum.  I didn't know a record had any voltage ;-)
> 
> > But --- we want to apply the idea to photographic prints.  Hmm!! How shall
> > we do this??   Density sure seems like an important concept but
> > the diagram
> > certainly doesn't have any labels that say "density", so what to do?
> 
> It also doesn't have a label for voltage either.  You are missing the
> importance of the diagram.  It is merely an example showing what largest and
> smallest are.

Sure its an example but without labels (explicit or at least implied) its totally
useless.  With a background in audio, its probably impossible to look at the
diagram without intuitively seeing a record needle track (for us older guys),
a speaker cone motion, a voltage oscillation or something similar.

If we try to use this diagram as an example for the print domain, don't you
need to put some labels on the axes??  How else can we look at the "largest"
label and tell what it measures?

> 
> This is just SO simple.  Dynamic range is a concept.  It does not apply to
> any particular thing, and because I, or anyone, uses an example of audio,
> does not mean it only applies to audio.
> 
> All that is required for dynamic range are the variables listed in the
> equation, largest signal and smallest discernable signal.  Largest meaning
> the absolute value of the overall signal, and smallest discernable signal
> being just what that means.

Yep, but you still have to DECIDE what constitutes "signal".  

> 
> > You've
> > come up with
> > a way to put density onto the signal diagram and so have I. We both had to
> > "interpret" the signal diagram as it applies to density.
> 
> I didn't have to interpret anything, the meaning of largest and smallest
> discernable signal are clearly defined.

Like I said: You still have to DECIDE what constitutes "signal". I.e what property
do we measure to plug into the equation.  You can't just say "density".
You're "largest" is Dmax - Dmin
Mine is just Dmax.
You're "smallest" variation within a single gray
Mine is just Dmin.

> 
> > The
> > trouble is we've
> > come up with different interpretations!!  There's nothing in the book that
> > addresses or supports one interpretation over another.
> 
> But that's just not true.
> 
> > You have CHOSEN what you think is the most obvious
> > interpretation, in fact it seems so obvious to you that its hard
> > to think of
> > it as a choice.
> 
> It is only obvious to me what it means, simply because I have worked with
> dynamic range for over 25 years, and it has been exactly the same every
> time, from the exercises in class, and professors and classmates that I've
> had discussions with, for the hundreds of engineers I've work with, and for
> the thousands of customers that have read my specifications, equations and
> analysis.  It's a pretty sound base!

Is that 25 years of experience in dynamic range of photographic prints??
Remember my issue is NOT whether you understand dynamic range in general,
I'm concerned with how it's applied to prints.

> 
> > First of all, I guess I have to convince you that we have both
> > made choices.
> 
> You can't do that, because my terms are not by choice.  They are, and have
> always been, clearly defined.
> 
> > If that works, we can agree to have different interpretations
> > leading to two
> > definitions of Dynamic Range
> 
> But any interpretation that does not match what I know dynamic range to be
> is wrong.  It won't be dynamic range.  I did not make up dynamic range, nor
> did I make up the definitions of the terms used in it.

You gotta realize that you know lots about dynamic range in one area, but
that applying it to a completely different area takes some decisions about mapping
concepts from one to the other.

> 
> > I contend that there
> > isn't mathematical
> > argument because both are sound, its just a difference
> > (better/worse) argument.
> 
> I don't understand how claiming largest means highest level of signal and
> smallest discernable signal means lowest level of signal is "sound".  If you

----> I guess poor choice of word.    Definition:  sound: valid

> use those definitions, you are not describing DYNAMIC range.  Your
> calculation will be in error.
> 
> Let's just talk about "smallest".  You CAN have a very high dMin, say 2, but
> have the ability to distinguish .1 density, can you not?  Also some of the
> definitions of dynamic range (the correct ones that is ;-) say noise is the
> smallest discernable signal, and for the most part, it is.  Given that, are
> you saying that dMin is simply noise?
> 
> > My idea is to show how you put the labels on the graph and how I put them
> > on the graph.  The signal diagram in the book looks like a
> > voltage sine wave
> > with time along the x-axis, right?
> 
> Yeah, but it isn't.  It's a record grove....and you can just take a single
> slice out of the diagram, it is not necessary to be a wave at all.

The groove gets converted to that at playing, right?  Try to play that groove
without moving it in time.  Can't take a single slice out of sound, can you?
You can't have sound without time.


> > You are looking at the large amplitude and putting dMin at the
> > bottom trough
> > and dMax at the top of the sine wave so that "signal" means (dMax-dMin).
> 
> Well, it doesn't matter if there is a picture of a sine wave or not.  The
> point of the example is to show the extents/bounds of the signal, and it
> doesn't matter if it's voltage or density.  I do agree that the two bounding
> limits can be equated to dMax and dMin, and the "largest" in the dynamic
> range equation, when applied to an image is dMax - dMin.
> 
> > Likewise, the  small amplitude is "soft" in audio language
> 
> Do you mean the vertical distance between the top and bottom of the "signal"
> (not the bounds)?  That is neither loud or soft.  Loud is if the signal is
> at the top of the bounds, and soft is if the signal is at the bottom of the
> bounds.  The, what I believe you are calling "small amplitude" has nothing
> at all to do with loud or soft.

Well if the diagram is a record groove, the loud music is when the groove swings
back and worth from the top bound to the bottom bound i.e. the amplitude
of the audio signal is max.  The soft music is where groove moves thru a
"small amplitude".  (Did you really say that small amplitude signal has nothing
to do soft (i.e. quiet) audio?? Did you?)  I'm sorry but I keep reading that
last sentence you wrote.  You do know how records work, don't you?


> > let me try with a
> > what the signal diagram looks like in both audio world and print
> > world.  In
> > audio its: loud section followed by soft section.
> 
> Sorry, you lost me.  I don't believe your terms "loud section" and "soft
> section" are really right...
> 
> > On the print I want it
> > to be a dark section followed by light section (i.e.  paper half
> > black and then
> > half white).
> 
> He he, that I understand ;-)
> 
> > In audio we talk about RMS Power output and it is max in the
> > "loud" section and min in the "soft" section.
> 
> As I've said, RMS etc. doesn't apply to dynamic range, but I'll see where
> you're going with this anyway...  It seems you are using '"soft" section'
> ambiguously.  Here it almost appears as you mean it as being a signal that
> is close to the bottom bounds...but above, you say...see **** above.
> 
> > And so in the print we have
> > density is max in the black section and min in the white section
> 
> Yes.
> 
> > --- and I
> > want signal strength to be exactly analogous to density.
> 
> Fine.
> 
> > ---  Question: what does your paper look like?
> 
> You said above the paper was half black, then half white...so that's what
> the paper looks like, right?
> 
> >  half high contrast and
> >  half low contrast?  It sure doesn't "feel" analogous to my audio
> >  example: half loud, half soft.
> 
> Where do you get "half" from?  You lost me here...
> 
> > The really weird thing about
> > contrast is that its JUST the transition.  There's no extent, it
> > can't keep going.
> 
> What do you mean by that?

The more I keep reading your responses, the more you seem to be glossing
over what you are doing.  You've referenced the signal diagram lots of times
saying it completely defines how to measure "signal".  You've got to relate
the squiggles in the diagram to something in the real world.  For audio
interpretation it has to MEAN something i.e. relate to sound.  I thought
the audio interpretation was obvious but the little loud/soft discussion above 
makes me wonder about even that.  The print interpretation is even more
abstract.  The diagram (or make a new one) somehow  has to relate to
a print i.e. show me what a largest signal versus a smallest signal looks
like on paper.  If you can't say what a "largest signal" looks like or
what a "smallest signal" looks like, how are you going to recognize it in
a print?   Briefly going back to the audio world, would you agree that
"largest signal" is the loudest sound you get from the speakers and
"smallest signal" is the quietest (noise included, of course)??
For me in the print world, my "largest signal" looks like pure black and
my "smallest signal" looks like pure white.  Can you describe yours
as simply?

> 
> 
> > Come on now.  There's lots of references to dynamic range as it applies
> > to the audio world.
> 
> Yes, because engineers design audio equipment, and because companies have to
> test this gear and produce specs for it, it is a specified piece of
> information.
> 
> > Where are the books about dynamic range as it
> > applies to prints?
> 
> Ansel Adams did ;-)  I am sure that the companies that make paper/chemicals
> etc. have information on this, and it may or may not be published.  This is
> a very different field than audio.  To expect there to be the same level or
> requirement of specsmanship in photographic paper/printing as there is in
> audio is really asking too much.  Most people who are interested in this
> type of information for prints are few and far between, but for audio it's
> every college kid...it's far more "pedestrian".
> 
> I am sure that somewhere dynamic range of prints is discussed.  I have about
> a dozen books on subjects that may contain some information on it...  The
> one book I'd start with is a well known "bible", "The Handbook of Modern
> Halftone Photography" by Ewald Fred Noemer.  It, unfortunately, has no
> bloody index...but it would be my first guess for a book that might discuss
> dynamic range with respect to photography.

Actually, I've looked at a few books that use the term "dynamic range" as
related to prints.  None have formal definitions, but all use it as
a  range (i.e. min and max) of useful zones, exposures, densities,
brightness/darkness, etc.


> 
> But Higgins shows the definition of dynamic range is...so it IS in a book!

  Certainly not for prints!

> 
> > Dynamic range is just the generic
> > term that
> > can be applied to many areas of study.
> 
> I believe it is a very specific property, as defined by the dynamic range
> equation.
> 
> > I don't
> > think they are "wrong" per se, but I definitely do think there are other
> > ways to interpret them and potentially have a more useful concept.
> 
> That's what I don't understand.  The definition you want to ascribe to it
> isn't useful, as we already have a term for that...density range.  To me,
> dynamic range is a very valuable property for imaging (as well as audio).

What you calculate may be valuable in some way, but I don't think its 
what others would use the term "dynamic range of a print" for. 

> 
> Phew!
> 
> Regards,
> 
> Austin

Phew is right!!
Regards,

Roy