Zone Placement

joh · Sep 8, 2011

ahh...now I understand what the graph's show and what you mean.
It's very interesting...i get a little bit stuck with the translation of
the word flare in this case
I never tried a "pre-exposure" but I see that it could realy be worth a mint,
espacially in scenes with high contrast and a 135mm camera.
Thanks for that tip.

espadrew · Sep 8, 2011

Where the zones are

In response to your questions: Are the zones on the negative? Are they on the paper? Are they in the scene? The answer is yes to all three. The 'zones' in the subject represent the subject's luminance range, in the negative they are represented by the varying densities from somewhere above Film Base + Fog to the maximum density of the film (D-Max), and same for the paper. The goal is to carry the subject luminance through to the paper, allowing of course for artistic interpretation.

RPC · Sep 8, 2011

There seems to be some confusion here on what a zone is. In Ansel Adam's Zone System, the term "zone" is used only when referring to film exposure. When referring to negative densities or print densities, he uses the term "values", not zones. Adams says that zones are one stop (an exact doubling or halving of exposure, or change of .3 subject reflection density units) apart. His system is based around this central idea. "Values" can be any distance apart based on many factors.

Stephen Benskin said:
In sensitometry, 0.30 is always a stop.

In sensitometry, a change of .3 density units on a negative is a doubling or halving of density, but I don't believe I have ever heard this use correspond to the term "stop". I believe a stop refers only to a doubling or halving of exposure, not a doubling or halving of film density.

Stephen Benskin · Sep 8, 2011

RPC said:
In sensitometry, a change of .3 density units on a negative is a doubling or halving of density, but I don't believe I have ever heard this use correspond to the term "stop". I believe a stop refers only to a doubling or halving of exposure, not a doubling or halving of film density.

It's common usage.

markbarendt · Sep 8, 2011

Stephen Benskin said:
Sounds more like a religion to me. Sorry that was flip. I was being flip with Kirk too. Basically, if there's no precision in a language, how can ideas be properly communicated?

Nope, no religion.

Math and physics are precise, art and language are not.

Stephen Benskin said:
According to Zone System testing, Zone I is four stops down from Zone V and Zone VIII is three stops up from Zone V. Sounds to me like the the Zones in the 7 stop range between Zone I and Zone VIII are divided into one stop steps.

If there is no difference between a zone and a stop, then there is no reason to use the word zone. If you want to talk with precision just stop using the word zone.

I've actually tried to reconcile that in my head and the explanation that fits is that in a standard contrast scene that spacing is true. The imprecision of language makes this idea a challenge to communicate.

If we use +2 development (to keep the math simple) it's only a 5-stop range (not 7) and zone V is not 4-stops up from zone I, it's only 3 stops up measured using a light meter. In this case Zone VIII is only 2-stops up from zone 5, not 3.

Stephen Benskin said:
And who ever said sensitometry isn't creative?

Not me.

Stephen Benskin · Sep 8, 2011

espadrew said:
The goal is to carry the subject luminance through to the paper.

That is what the curve examples are about. How do the values move through the process. In this particular case, from the subject to the film illustrating a common misinterpretation of the interpretation of the illumininace range.

I'll be posting at least one example of a four quadrant reproduction curve to place it in context.

Stephen Benskin · Sep 8, 2011

markbarendt said:
Nope, no religion.

Math and physics are precise, art and language are not.

Tone reproduction can be define and is a science. Making a photogaph and how it all comes together is an art. I don't think talking about how one works diminshes the other. They complement each other, and I've found I have greater control over the outcome the more I know. Why do people think there's a need to remind everyone the photography is an art form?

in a standard contrast scene that spacing is true.

I'm not sure what you mean by that.

Stephen Benskin · Sep 8, 2011

No offense taken. I agree with you're saying. I just like talking about theory. This usually means focusing on the finer points. For example, there's nothing wrong with the different methods of exposure determination (eg Zone System speed testing), I just like to make a distinction between them and film speed determination.

If you distill down this thread into a practical testing procedure, then I would have to say, when doing in camera Zone System testing for contrast determination, meter Zone V and open up two stops. Find the exposure that falls 1.05 to 1.10 over 0.10 over Fb+f. Or know that if continue to use the traditional approach where you open up three stops and use 1.25, that it will still give you the correct contrast for the film, it doesn't represent the negative density range that will be produced.

RPC · Sep 8, 2011

Stephen Benskin said:
It's common usage.

Could you point me to a documented example?

RPC · Sep 8, 2011

markbarendt said:
If there is no difference between a zone and a stop, then there is no reason to use the word zone. If you want to talk with precision just stop using the word zone.

A stop refers to a specific exposure change, a zone a specific exposure level. Zones are a stop apart.

Stephen Benskin · Sep 8, 2011

RPC said:
Could you point me to a documented example?

Personally, I don't like using Zone terminology as a general rule. I kind of had to in this thread. Yuck.

First when I said common usage, I meant something more along the lines of common vernacular. Anyway, I've attached two documents that I think is what you are asking for.

One is a page from Photographic Materials and Processes by Strobel et al. The other is an internal CI chart from the R&D department at Kodak.

As the CI chart is sort of connected with the concepts of this thread, I have a challenge to present. Anyone know how the CI values were produced? What were the factors involved? Bonus points for an analysis of any strengths or weaknesses of the model.

markbarendt · Sep 8, 2011

Stephen Benskin said:
Tone reproduction can be define and is a science. Making a photogaph and how it all comes together is an art. I don't think talking about how one works diminshes the other. They complement each other, and I've found I have greater control over the outcome the more I know.

I don't disagree, in fact I would encourage learning more.

Stephen Benskin said:
Why do people think there's a need to remind everyone the photography is an art form?

My point is not that photography is an art.

My point is that "1-stop = 1-zone" is only true where there is a normal brightness range scene, where the film is exposed normally, developed normally, and zone 2 paper is used for the print. Change the contrast of the film (expand/contact) or the paper grade and the portion of the negative that gets printed changes, the 1:1 relationship is lost.

markbarendt · Sep 8, 2011

RPC said:
A stop refers to a specific exposure change, a zone a specific exposure level.

Those are very reasonable thoughts

RPC said:
Zones are a stop apart.

The paper defines where the zones land.

Zones run from pure black "0" to pure white "X" on paper. That is true regardless of the paper grade, all the zones exist regardless of how hard or soft the paper may be.

A harder paper will print a shorter contrast range, fewer stops from the negative, than a normal paper. A softer paper will print more stops from the negative.

Minus film development allows us to fit more stops from the scene onto a normal paper, plus development helps us fit fewer stops from the scene onto the normal paper.

Regardless of how much of the negative is printed, there are still ten zones available on the paper.

Regardless of how many stops existed in the original scene, there are still ten zones available on the paper.

Bill Burk · Sep 8, 2011

Stephen Benskin said:
Personally, I don't like using Zone terminology as a general rule. I kind of had to in this thread. Yuck.

I know you prefer reasoned sensitometry to Zone System and work ceaselessly to encourage thoughtful use of it to those who want to use the Zone System.

Stephen Benskin said:
As the CI chart is sort of connected with the concepts of this thread, I have a challenge to present. Anyone know how the CI values were produced? What were the factors involved? Bonus points for an analysis of any strengths or weaknesses of the model.

I can give a strength of ***this model*** that I bet you never thought of. I graph my curves on paper. And I use a CI transparency overlay to read the graphs.

With more sensitive film, the sensitometer tends to "overexpose" the film being tested when using a 21-step test wedge. Any faster than 400 and I won't have a toe on my graph and I may not even have an 0.1 density reading to gauge speed by.

But my CI index will fit nicely on the graph. So I will know my CI.

***Thought you were talking about CI 'per-se'.

Now that I've printed the chart I know you are talking about something else.

This is same as Zone system except not using Zones at all. Not using N+ or N- either. Just tells you what to develop to if you want to get a print matched to the negative based on your meter reading. Nice. I was going to extrapolate something like this anyway since it is easy for me to develop to a CI.

Stephen Benskin · Sep 9, 2011

Okay Bill, chose a value on the chart. How did they arrive at that number?

Bill Burk · Sep 9, 2011

When I take a paper with LER 0.9 (Galerie 3 in my hands) and follow the 0.50 CI curve on paper from 0 to 7 stops (Zone 0 to Zone VII at N), I arrive at my LER 0.9 in 7 subject light meter stops.

But on the chart, that isn't where 0.50 CI is prescribed, it's 2/3 stop to the right at 7 2/3 subject light meter stops.

0.56 is the prescribed CI.

Oddly (or not - depends how you see things), <N> that I wrote on my graph, is on the 0.56 CI curve where it crosses Zone VII. I put that <N> there after working with you to incorporate flare.

Stephen Benskin · Sep 9, 2011

Flare, eh? And...

Check out the CIs from the processing tables in this Kodak Xtol data sheet. They start on page 6. What does it have as Normal? Where does that fit into the CI chart? Don't try and figure out the pluses and minuses they have for Xtol just yet. It will just confuse you as they don't match up with the Kodak CI chart. Bonus if anyone can figure that one out.

I hope you see where I'm going with this. This is not trick. It's like I said earlier, the key is in the interpretation of the data, and a large part of that is having a good grasp of certain principles and asking the right questions. Hint: How is CI calculated?

I'm tempted to start a new thread with this except that it also fits in well with the Zone System / Tone Reproduction negative density range question.

markbarendt · Sep 9, 2011

Okay

So using the method for determining CI found in Kodak's Sensitometry Workbook the curve used in the examples has a CI of 0.58. Close as I can tell.

The placement of the zones can be determined by the paper's range, if the papers printable range is 1.05 then B should print the zones as expected and A would end up clipping.

Am I missing something with regard to the paper's characteristics?

markbarendt · Sep 9, 2011

Yes CI is a measure of the slope.

markbarendt · Sep 9, 2011

That's why I said "a" and not "the".

Stephen Benskin · Sep 9, 2011

Looks like a new thread on CI and average gradients would be a good idea. The use of the curve gradient is an important element in the explanation of the two curve examples, but a detailed discussion about gradient methods will just make this thread more convoluted. Anyone want to start up the new thread?

pbromaghin · Sep 9, 2011

Wow.

I've quadrupled my photographic knowledge in the last couple of years and this thread only serves to show how ignorant I remain.

Many thanks to all of you with the really large brains.

markbarendt · Sep 9, 2011

Stephen,

How about a summary of what we were "supposed to get here" before we move on.

Stephen Benskin · Sep 9, 2011

Working on it.

Bill Burk · Sep 9, 2011

Wait, don't make it too easy. I still haven't figured out the puzzle...

Zone Placement

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