Digital BW, The Print

----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 7:16 PM
Subject: RE: [Digital BW] Dynamic Range Definitions and Print Tones


> Hiiiii again Martin ;-)
>
> > Since Ansel Adams and Minor White worked out the zone system and by
> > definition of the term dynamic range
>
> Do you have a reference for EXACTLY what you claim?  I AM a Zone boy (as
in
> I do all Zone work, with development compensation etc.), and I see that
the
> Zone system has some basis in dynamic range, simply by defining 10 steps,
> that's giving it SOME dynamic range...

I think Mike already posted to that.
>
> > From NASA website:
> > From the Cornell University Library:
> > From Digital Photography Review:
>
> And you conveniently left out the ones that were "better" ;-)  Why do you
> keep going back to taking some one's interpretation of a REAL EQUATION and
> not just use the real equation?  Talk about adding noise to the system!

Okay I will add:

From X-rite\ufffds \ufffdThe Color Guide and Glossary\ufffd

\ufffdDynamic Range: An instrument\ufffds range of measurable values, from the lowest
amount it can detect to the highest amount it can handle.\ufffd


and:

From CCD Direct:

\ufffdThe dynamic range is often represented as a log ratio of well depth to the
readout noise in decibels. For example, a system with a well depth of 45,000
electrons and a readout noise of 15 electrons would have a dynamic range =
20 log (45,000/15), or 69dB.\ufffd

http://www.ccddirect.com/online-store/scstore/dynamic.html



You never did say what you thought of this last one which seems to be in
your field.

>
(snip)

>
> It is defined by the equation...we are going around in circles here...



Yep. I am rather dizzy.
>
> >
> > You have not been able to supply a value for the noise in your
> > equation yet
> > so how did you manage that.
>
> Er, yes I did.  I gave you an example using 0.01D as the "noise".



Hmmm. Somehow an example just doesn't satisfy like an experimental value.
What if I say for example that the noise in a silver print is
0.00000000000000001 dB can I use that? <G>
>
(snip)

>
> You can NOT take someone's interpretation of an equation and just write
the
> equation from that!  My God.  As I've said a dozen times, and you, for
some
> reason won't get it, the dynamic range equation IS the equation for
dynamic
> range, period.  No matter how many times some pedestrian has tried to put
> verbosity to it to try to describe it TO LAY PEOPLE using ambiguous terms.



You say they are lay people or it is a simplified explaination and I don't
agree. I think we are not going anywhere in this direction.
>
> > (snip)
> > Austin, I offer you a chance to look at what might be the noise value of
a
> > print to use in your equation and you tell me that is irrelevant to the
> > overall discussion? If you cannot give this term a value than how can
you
> > determine if your dynamic range tells you something significant about a
> > print?
>
> The point is there IS noise, it exists everywhere.  We do not have to
> quantify it to know it exists.  It is also not a far stretch to believe it
> is significant, knowing the difference in reflectance that paper has
alone!



I have no reason to believe that noise exists everywhere and I can't take
that as a given. The noise you described earlier would be variations within
a given paper base rather than the variation from brand-to-brand and may be
so small as to push the results of your equation towards infinity.
>
(snip)

>
> We are not in disagreement on how to derive the density range...and that
> wasn't the important part of what I was saying, the next paragraph is.
>
> > >
> > > For dynamic range, take dMax (from your density range measurement) and
> > > subtract your dMin (from your density range measurement), and that
gives
> > you
> > > "max" for the dynamic range equation.  "min", basically, will be the
> > > variance across the patch that I've suggested above.
> >
> > Okay, looks like the density range (or the log expression of ratio of
the
> > reflectance) divided by the noise.
>
> YES.  Grrr.  As you said, and I quote: "I have been saying that for post
> after post." ;-)
>
(snip)

> >
> > Just that it varies from light to dark so that you could not take a
simple
> > seperation between discernable tones but would need to mathematically
> > account for this variation.
>
> Sure, but again, that's just an implementation detail ;-)



Well I am a very practical engineer. Chemical process and project
engineering remember, so I want to know all those details.
>
(snip)

>
> Who said it can't be implemented?  Not I!



True but you need a meaningful value for the noise to do that.
>
> > If you don't have the
> > values you
> > need to apply your dynamic range equation, what use is it?
>
> Having a "correct" value or not doesn't mean it doesn't exist!
>
No but lack of a correct value makes it of little practical use.



> > And this had nothing to do with the operator but only the materials. <G>
>
> I was a VERY good B&W printer in the darkroom.  If it did have anything to
> do with operator, it was negligible.  I was a real purist, with very good
> equipment (still have it BTW, need to sell it ;-) and knew how to use it,
as
> I do my scanner.



I did not mean to impugn your printing skills. I am proud of my own
abilities but still manage to have some real disasters.
>
> Do you ever sleep?



No. That would be terrible ineffiecient and waste of valuable time.  <G>



I'm just on the west coast and a bit of an insomniac, and can keep posting
past your bed time but you leave me a whole stack to look at with my morning
coffee.



Martin