Do you test your film for true ISO?

cluttered,

Take a close look at Stephen Benskin's post, he has provided the solution to the riddle but left some of the numbers unlabeled. You should try to "label" them in your own mind, because I think that's not a difficult exercise. I think his answer is right.

I have always wondered about why some books recommend what looks like a 1.3 negative density range when the paper needs a 1.05 negative density range.

The test you are doing (wherever you found it is still a big mystery) is testing "correctly" in terms of the result.

But in reality you are aiming for a 1.05 negative density range with your test, and the explanation is in Stephen Benskin's post.

Now I am going to look at where my idea of what's happening is just slightly different than Stephen's, I think he'd agree with this minor revision

Stephen Benskin said:

Instead of counting to the right 2.10 log units from 0.10 on the film's characteristic curve, then searching for the density at that point. Subtract 0.30 for flare from 2.10 and count only 1.90 log units. Now find the density at that point. Chances it will be around 1.15. 1.15 minus 0.10 = 1.05 which is the aim we are looking for. These values for the variables reflect reality. An aim negative density range of 1.05, and a log-H range of 2.10 - 0.30 = 1.90.

1.05 / 2.10 - 0.30 = 0.58

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Stephen's explanation
1.05 negative density range of Zone I to probably Zone VII / 2.10 exposure range Zone I to Zone VIII - 0.30 flare

My explanation
1.05 negative density range of probably Zone II to Zone VIII / 2.10 exposure range Zone I to Zone VIII - 0.30 flare

Reason for this slightly different explanation:

Flare raises the shadow density and leaves highlight density pretty much alone.

Flare is what takes a shadow density that you placed on Zone I up higher... So what you placed on Zone I actually arrived at Zone II.

cluttered, even if you didn't test for Zone II, you might have a negative with the density for Zone II on one of your other test frames. If you had an exposure index test shot for Zone I that happened to be shot at one stop more exposure than the "winner" (the one that measured 0.10) of the exposure index Zone I test.

Due to flare, this is what will really turn up on your pictures: deep, unmeasured shadows that you thought should fall on Zone I, will really land on Zone II which might probably be around 0.25 density.

Then the model for your negative density range (NDR) is 1.3 (your Zone VIII density) minus 0.25 (Zone I fell on Zone II where flare took your shadow density) = 1.05 NDR

Michael R 1974 said:

... this difference has little if anything to do with individual processes/procedures. It is not a personal calibration that takes our individual preferences into account. It's just a different measurement, which means there is no new information revealed by the test.

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Nicely thought out.

Of course there are things in your process that might vary, and if you can measure speed, even just relative speed, it gives you a point of process control. Some people recommend measuring pH of the developer too. Not a bad idea. Both are easy tests.

I found a source for the 1.30 density expectation for Zone VIII.

None other than Ansel Adams himself, in The Negative.

All the Normal graphs cross about 1.30 at Zone VIII and he mentions in text that he's looking for 1.25 to 1.35 density.

Now I've often thought that he didn't account for flare in the Zone System, because he didn't explain how he handles flare.

But there it is... He handles flare by choosing a density for Zone VIII that makes way for flare to raise the density of the shadows.

Michael R 1974 said:

I agree, Bill. Actually my comment had to do with EI rather than process control. Understanding the nature of the difference between ISO speeds and the EIs determined using the Zone System was a minor revelation to me. Barring extreme procedures, it rendered the EI test unnecessary. I realized I know what my Zone System EI will be just by looking at the box of film, that the difference between that EI and ISO would always be the same within experimental error, and that (contrary to what many writers would have us believe) this difference has little if anything to do with individual processes/procedures. It is not a personal calibration that takes our individual preferences into account. It's just a different measurement, which means there is no new information revealed by the test.

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Sorry, but I disagree. I do get a true 160-200 speed out of FP4+ in Sprint developer, but only 250 out of HP5+ in Sprint. Same meter, same LF lenses/shutter, same technique. I did repeat the test 4 times with FP4+ and a couple of times with HP5+ and measured using two different densitometers. I get internally consistent results and my shadow detail does suffer if I shoot HP5+ at box speed but not if I shoot FP4+. Personal film speed testing is useful to yourself, but probably not applicable to others.

haziz said:

... following the methodology described by Fred Picker in his Zone VI Workshop, which is itself based on the work of many other photographers. I never do a Zone VIII film developing test for developing time..

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A Zone VIII film developing time test would help (or any other test of contrast). How do you test contrast?

haziz said:

... I do get a true 160-200 speed out of FP4+ in Sprint developer, but only 250 out of HP5+ in Sprint. Same meter, same LF lenses/shutter, same technique. I did repeat the test 4 times with FP4+ and a couple of times with HP5+ and measured using two different densitometers. I get internally consistent results and my shadow detail does suffer if I shoot HP5+ at box speed but not if I shoot FP4+..

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I love a good riddle.

Do you develop FP4+ for 8:30 and HP5+ for 10:00? If you develop both for 10:00 that could explain your results.

The two films do have quite different spectral response curves. Since FP4+ has more red sensitivity, late afternoon light or tungsten could cause your discrepancy. (If you are testing with flash or full blue daylight, the spectral response would tend to cause the opposite of your finding).

Bill Burk said:

cluttered,

Take a close look at Stephen Benskin's post, he has provided the solution to the riddle but left some of the numbers unlabeled. You should try to "label" them in your own mind, because I think that's not a difficult exercise. I think his answer is right.

I have always wondered about why some books recommend what looks like a 1.3 negative density range when the paper needs a 1.05 negative density range.

The test you are doing (wherever you found it is still a big mystery) is testing "correctly" in terms of the result.

But in reality you are aiming for a 1.05 negative density range with your test, and the explanation is in Stephen Benskin's post.

Now I am going to look at where my idea of what's happening is just slightly different than Stephen's, I think he'd agree with this minor revision





Stephen's explanation
1.05 negative density range of Zone I to probably Zone VII / 2.10 exposure range Zone I to Zone VIII - 0.30 flare

My explanation
1.05 negative density range of probably Zone II to Zone VIII / 2.10 exposure range Zone I to Zone VIII - 0.30 flare

Reason for this slightly different explanation:

Flare raises the shadow density and leaves highlight density pretty much alone.

Flare is what takes a shadow density that you placed on Zone I up higher... So what you placed on Zone I actually arrived at Zone II.

cluttered, even if you didn't test for Zone II, you might have a negative with the density for Zone II on one of your other test frames. If you had an exposure index test shot for Zone I that happened to be shot at one stop more exposure than the "winner" (the one that measured 0.10) of the exposure index Zone I test.

Due to flare, this is what will really turn up on your pictures: deep, unmeasured shadows that you thought should fall on Zone I, will really land on Zone II which might probably be around 0.25 density.

Then the model for your negative density range (NDR) is 1.3 (your Zone VIII density) minus 0.25 (Zone I fell on Zone II where flare took your shadow density) = 1.05 NDR

Click to expand...

Bill, you're right, I short handed it and gave the wrong impression.

Stephen Benskin said:

Bill, you're right, I short handed it and gave the wrong impression.

Click to expand...

It's a non issue...

The most interesting thing I see tonight that I didn't see yesterday is that "Normal" in Ansel Adams The Negative is so close to the flare-adjusted normal standard model... That I might be able to say that the Zone System (as documented in The Negative) actually does deal with flare.

Bill Burk said:

I found a source for the 1.30 density expectation for Zone VIII.

None other than Ansel Adams himself, in The Negative.

All the Normal graphs cross about 1.30 at Zone VIII and he mentions in text that he's looking for 1.25 to 1.35 density.

Now I've often thought that he didn't account for flare in the Zone System, because he didn't explain how he handles flare.

But there it is... He handles flare by choosing a density for Zone VIII that makes way for flare to raise the density of the shadows.

Click to expand...

Sorry Bill, I think you are having a little confirmation bias here. Just because something happens to work doesn't mean the explanatory theory is correct. Adams gives the 1.15 to 1.25 range and never mentions anything about it including flare compensation. He never says anything about testing for the 1.15 to 1.25 range but expecting the range to be shorter in practice.

Adams actually believed testing with a camera introduced flare, so odds are he thought flare was already part of the test exposure. This is stated in The Negative. Why would he then add an additional compensating factor? As I've previously explained, as defined the Zone System in camera test is practically a no flare test. What we have with the Zone System is a classic case of a no flare test being used as if it represented practical use. Adams is using the full 7 Zone range, not a six Zone range which he should if he was factoring in flare.

Sensitometric testing uses a no flare film characteristic curve, but factors in flare when extrapolating shooting conditions.

The higher aim density happens because of the 2/3 over exposure resulting from the Zone System speed test.

Stopping down four stops from the metered exposure point places the exposure 2/3 stop below 0.10. From 0.10 to the highlight, the density range is around 1.05 in this example.

Note: Exposure theory has the shadow exposure falling 4 1/3 stops from the metered exposure point. Normal flare will bring it up around the speed point which falls 3 1/3 stops below the metered exposure point.



Making the usual 2/3 stop adjustment resulting from Zone System testing will shift the curve to the right. The highlight density range is now 1.15. Flare reduces the log-H range, so you don't measure the resulting density range for 7 stops, but 6 stops. What makes the numbers not work out perfectly is that the Zone System uses 7 stops and the standard model uses 7 1/3 which has been determined to be the statistical average.



What's more realistic? Adams found that when the test's aim negative density range was 1.15 to 1.25, the resulting negatives in practiced tended to print on a grade two, or that he intentionally choose the higher than normal aim numbers knowing flare will compensate and just didn't want to tell anybody.

I absolutely believe he selected the aim density range because in practice they printed on grade two. I believe when he incorporated flare this way, he didn't realize that's what he was doing. As you say, he thought the camera test had flare.

I don't think we will find flare incorporated in the first Zone System manuals, such as Minor White's booklet.

When White, Zakia and Lorenz got together for the New Zone System Manual, there is some mention of flare... and they explain how they deal with flare...

"To help overcome the effect of flare is the reason that Zone III is placed just off the toe of the negative curve, and that the film is developed so that Zone VII falls just below the shoulder."

Now in that manual, they explain manufacturer's data sheets, and they recommend for Zone System Normal N a Contrast Gradient 0.50 - 0.55. But they mention the figures disregard flare.

This seems pretty messy to me. But there is some realization that flare is an issue at least.

Bill Burk said:

I found a source for the 1.30 density expectation for Zone VIII.

None other than Ansel Adams himself, in The Negative.

All the Normal graphs cross about 1.30 at Zone VIII and he mentions in text that he's looking for 1.25 to 1.35 density.

Now I've often thought that he didn't account for flare in the Zone System, because he didn't explain how he handles flare.

But there it is... He handles flare by choosing a density for Zone VIII that makes way for flare to raise the density of the shadows.

Click to expand...

I thought Adams originally used an 8 Zone system and later changed it to 10. Did he change his graphs when he did that?

Perhaps you should confirm your findings with John Sexton who'll put you straight on the matter.

RobC said:

I thought Adams originally used an 8 Zone system and later changed it to 10. Did he change his graphs when he did that?

Perhaps you should confirm your findings with John Sexton who'll put you straight on the matter.

Click to expand...

Page 220, The Negative.

Zone I to Zone VIII is a 7 stop difference.

In another thread I mentioned the multi-faceted nature of photography. Here is an example of another facet - the technical one concerning exposure, that some folks find satisfaction in gaining a nuanced understanding of. Not me, but I have an admiration for those that do!

Stephen Benskin said:

Page 220, The Negative.

Zone I to Zone VIII is a 7 stop difference.

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Yes I know, we've been here before. What he said and what his graphs show do not make sense when you apply his ideas of a 10 stop range printing from black to white at G2.
I have resolved that for myself with the way I work. Others are trying to bend the numbers to make them fit when they should really be bending the development if they want it to work the way adams says and not the way his charts show.

The problems is one of number following instead of following ones instincts. Leave the numbers behind and it all seems to work fine.

RobC said:

Yes I know, we've been here before. What he said and what his graphs show do not make sense when you apply his ideas of a 10 stop range printing from black to white at G2.
I have resolved that for myself with the way I work. Others are trying to bend the numbers to make them fit when they should really be bending the development if they want it to work the way adams says and not the way his charts show.

The problems is one of number following instead of following ones instincts. Leave the numbers behind and it all seems to work fine.

Click to expand...

Yes, we've gone over the accent black and specular white before and I've pointed out why testing includes the points they do - 7 stops for ZS and 7 1/3 stops for tone reproduction.