Zone system mathematically inconsistent

Stephen, I am suspicious that the scale marked "reflectance" covers a range of 100%. I've always assumed the scale of subject luminance range exceeds 100% by at least 2 stops because it represents subject in main light and subject in shade. Is that scale "reflectance" on the print?

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Bill Burk said:

Stephen, I am suspicious that the scale marked "reflectance" covers a range of 100%. I've always assumed the scale of subject luminance range exceeds 100% by at least 2 stops because it represents subject in main light and subject in shade. Is that scale "reflectance" on the print?

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Bill, the range covers the statistically average log 2.20 range. Like Holm wrote, it is from diffuse highlight to shadow detail and not specular highlight and accent black (which do exist). The idea is to fit the 2.20 subject luminance range into the paper's LER.

Paul Howell said:

Don't think any US Governmental Agency is using much if any film, other than for archive. When I was shooting for the Air Force we used Kodak, GAF, (which we all hated) and a mystery film rated at 200, made in USA without a trademark. It was rather good black and white, I assumed it was Dupont made to order for the DOD, and I recall seeing bulk rolls of 3M E6. The recon guys had their own stock.

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Might have been Haloid made by the parent company of Xerox before the copy machine.

PE

Stephen Benskin said:

Bill, the range covers the statistically average log 2.20 range. Like Holm wrote, it is from diffuse highlight to shadow detail and not specular highlight and accent black (which do exist). The idea is to fit the 2.20 subject luminance range into the paper's LER.

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OK that's fine. I'll interpret it as the lower Zones being in shade. So reflection density over 2.0 and percentage under 1% is possible, when you know that the thing isn't really something with super-black ability in main light reflecting 1%... it's more like something that reflects an ordinary 5% but being situated in the shade... the amount of light measured can work out to be the equivalent of something reflecting less than 1% of the main light.

Bill Burk said:

OK that's fine. I'll interpret it as the lower Zones being in shade. So reflection density over 2.0 and percentage under 1% is possible, when you know that the thing isn't really something with super-black ability in main light reflecting 1%... it's more like something that reflects an ordinary 5% but being situated in the shade... the amount of light measured can work out to be the equivalent of something reflecting less than 1% of the main light.

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It's also Reflectance which involves a Lambertian surface and pi.

Don't make a mountain out of a mole hill. The Zone System is nothing more than a shorthand model with each Zone calibrated one EV apart for sake of meter reading and general convenience. How this fits onto the curve of any specific film, exposure, and development regimen differs widely and must be experimentally adapted to your own preferences via testing and printing. If you need precise results, get a densitometer and plot the film curves yourself. But all of this Zone System talk basically boils down to : exposure for the shadows (after reading them with your meter and placing the that somewhere well below middle gray (depending on the specifics), and then developing for the highlights (again, depending on the specifics). Since films as well as scene contrast range varies, you need to learn how to bend Zone theory to fit. It's not written in stone like the decalogue of Moses; not did God create the world in eight distinct zones. It's just a convenience tool.

Thanks, Drew. I am getting less interested in the picking of nits these days.

DREW WILEY said:

Don't make a mountain out of a mole hill. The Zone System is nothing more than a shorthand model with each Zone calibrated one EV apart for sake of meter reading and general convenience. How this fits onto the curve of any specific film, exposure, and development regimen differs widely and must be experimentally adapted to your own preferences via testing and printing. If you need precise results, get a densitometer and plot the film curves yourself. But all of this Zone System talk basically boils down to : exposure for the shadows (after reading them with your meter and placing the that somewhere well below middle gray (depending on the specifics), and then developing for the highlights (again, depending on the specifics). Since films as well as scene contrast range varies, you need to learn how to bend Zone theory to fit. It's not written in stone like the decalogue of Moses; not did God create the world in eight distinct zones. It's just a convenience tool.

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Good advice.

I actually have a densitometer and have been doing some film testing.

Also, I think an important part of the zone system was to try to adjust the scene contrast as expressed on the negative so that it would print well on normal contrast paper. With wide-ranging variable contrast papers available today, as well as the fact that a lot of people are doing hybrid processes where they can adjust the contrast easily with a computer, maybe much of the motivation for using the zone system has dissipated. Nevertheless, I still think there are some useful ideas to be gleaned from the zone system and adapted to one's own craft.

Question: Did Adams himself make wide use of the zone system in a formal sense in his own work, or did he use it mostly as a teaching device for his students?

It would be best to ask someone like Alan Ross or John Sexton that question, since they were assistants to Ansel. I never knew him personally, and the only exhibition I ever split with him was a posthumous retrospective right after his death. I suspect many artists bend their own manifesto doctrinaire rules. Minor White took the Zone System to the extreme of almost a gray-scale religion, but he even looked like the nutty professor in Back to the Future. I regard the Zone System as a valuable teaching tool as well as a convenient common-denominator mode of communication in situations like this forum. But after awhile, with experience such things become almost second-nature and fade in the rear-view mirror. To fluidly photograph you need to do so intuitively, and not be futzing around at the time of the shot with formulas and calculators and so forth. But the ability do a level of post correction in a computer with something like PS, or tweak contrast using VC papers, doesn't help if enough information isn't on the negative to begin with; so the Zone System is equally applicable in those cases too. But, as they say, there is more than one way to skin a cat.

As one who has eaten the Jell-O shots I can say it provides a mnemonic to help you plan what you are doing.

I use Zone System all the time in the field with a camera, in little ways.

But I don’t ask my wife to make my toast Zone IV though. That was a step Minor White took too far.

Photo Engineer said:

Might have been Haloid made by the parent company of Xerox before the copy machine.

PE

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By the way, I once worked for Battelle Memorial Institute, which was instrumental in the development and commercialization of the Xerox process. Largely as a result of the money made through it's connection with the Xerox process, Battelle became the largest private research institute in the world.

And our CTO and Director of Research spent some time at Battelle after he retired. He then re-retired and is now re-retired in the deep south!

PE

Hi Bill. My Dad always preferred his toast on Zone II, and so did his younger brother, whom he raised after their father died. I like mine Zone VII.

DREW WILEY said:

Hi Bill. My Dad always preferred his toast on Zone II, and so did his younger brother, whom he raised after their father died. I like mine Zone VII.

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I like my toast sepia toned - with butter.

Ran across this the other day. There are three exposure models showing reflection density and Reflectance. The first is keyed off 18% Reflectance. The second is keyed off 12% Reflectance, and the third is keyed off the diffused highlight of 100% Reflectance. The third model is the one that works best with exposure theory math.

Stephen Benskin said:

Ran across this the other day. There are three exposure models showing reflection density and Reflectance. The first is keyed off 18% Reflectance. The second is keyed off 12% Reflectance, and the third is keyed off the diffused highlight of 100% Reflectance. The third model is the one that works best with exposure theory math.

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Interesting.

It looks like the zones are listed in backwards order in the Standard Model. By the way, the term "Standard Model" sounds like something from particle physics.

Stephen Benskin said:

Ran across this the other day. There are three exposure models showing reflection density and Reflectance. The first is keyed off 18% Reflectance. The second is keyed off 12% Reflectance, and the third is keyed off the diffused highlight of 100% Reflectance. The third model is the one that works best with exposure theory math.

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How can Zone V be 18%, 12% and 6% reflectance? They all can't be middle gray.

faberryman said:

How can Zone V be 18%, 12% and 6% reflectance?

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I think it partly a manifestation of my point that the zone system is mathematically inconsistent, together with a dose of ill-defined parameters.

As far as the 6% us concerned, it looks like the zones are counting backwards in the standard model.

Reflectance goes down as density goes up.

alanrockwood said:

I think it partly a manifestation of my point that the zone system is mathematically inconsistent, together with a dose of ill-defined parameters.

As far as the 6% us concerned, it looks like the zones are counting backwards in the standard model.

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Good catch. My bad. The header should just be "Step." Exposure theory doesn't normally use Zone nomenclature.

I did steal the term "standard model" from quantum physics. Technically, it's the statistical average model.

Much better, thanks Stephen.

PE

alanrockwood said:

By the way, I once worked for Battelle Memorial Institute, which was instrumental in the development and commercialization of the Xerox process. Largely as a result of the money made through it's connection with the Xerox process, Battelle became the largest private research institute in the world.

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I went to grade school in a big 3 story brick building from 1880's era. We had a mimeograph machine in the secretaries office. Sometimes we would get the blue inked copies and the solvent wasn't quite dry. The pages would be cool, and I remember smelling the solvent..

alanrockwood said:

I think it partly a manifestation of my point that the zone system is mathematically inconsistent, together with a dose of ill-defined parameters.
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Adams was never as technical as his reputation suggests. The problem with the Zone System vs Tone Reproduction is the Zone System has some assumptions that differ. One of the results is the Zone System EI rarely equals the ISO speed. While it was in closer agreement prior to the 1960's film speed change, the underlying assumption was still off. Film speeds before 1960 were around 1/2 to 1 stop slower resulting from the inclusion of a safety factor. The 1960 standard eliminated most of that factor. The principles from that standard haven't changed. Since the Zone System never changed its testing procedures, a 1/2 to 1 stop difference in speed between the two methods exists. Contrary to the 50 plus years of speculation, Zone System testing doesn't represent the true film speed, nor do the film manufacturers tweet their results to make the films look better. And laboratory test can equate to real world results.

The idea of metering a target and stopping down to determine film speed, while prone to experimental error, can be a generally effective method, but only when the relationship between the metered exposure point and the film speed point is known. The Zone System's four stops down from the metered exposure point is simply different from the ISO's 3 1/3 difference between Hm and Hg. Exposure at the metered point is 8 / Hg. For a 125 speed film, Hg = 8/125 = 0.064 lxs. Per the ISO speed equation, film speed calculated as 0.8 / Hm. For a 125 speed film, 0.8/Hm = 8/125 = 0.0064 lxs. The difference between Hg and Hm is 10X, 1.0 log-H, or 3 1/3 stops. The Zone System's 4 stops or 1.20 log-H will fall below the speed point. No conspiracy. Just two different methods. One of which, never accurately defined itself.

The 1/2 to 1 stop increase in exposure with the Zone System, makes Zone V effectively 18% Reflectance, but only under statistically average conditions or in scenes with certain tonal distribution Of course, as the negative is over-exposed, any adjustments to compensate for it in printing will negate the alignment with 18%.

Zone System assumes it incorporates flare in the testing because incorporates a camera's optical system in the test. This might appear to be a logical assumption except flare is caused by scattered light from the higher luminances to the lower luminances. Zone System testing includes a single toned target, usually middle gray. Even under normal flare conditions, flare at the exposure mid-point is small compared to the shadows. In combination, in camera testing would produce little to no flare. Under statistically average conditions, normal flare is about a stop. In practice, the resulting exposure based on Zone System testing will be even higher with the addition of flare.

Flare also comes into play when determining an aim gradient or negative density range. While in practice, the difference between the statistically average luminance range of 2.20 and the Zone Systems 2.10 is only a 1/3 or a stop, the shorter Zone System range can cause problems with the math. A scene with a luminance range of 2.20 logs will have an illuminance range at the film plane of 1.90 logs. Development is determined by what the film sees. Kodak considers normal development to be between CI 0.56 and 0.58. Aim Contrast Index = Negative Density Range / Log Subject Luminance range - Flare. If the aim CI is 0.57 and the average scene is 2.20 log units, the aim negative density range is 1.25. Adam's The Negative has around 1.25 as the aim for a normally developed negative. The CI aim for the Zone System corresponds to Kodak's, except the Zone System doesn't factor in flare and Kodak does, and Kodak has a resulting density range of 1.05 for a normal negative. Again, the Zone System has made an assumption which is technically inaccurate, but renders good results. For one, the Zone System uses a luminance range 1/3 stop smaller than the statistically average. Moving 2.10 log units to the right of the fixed density point of 0.10 will indicate a higher density range than a point 1.90 log units from 0.10, but the gradient of the curve is the same. The only difference is how the numbers are determined, not which method best represents reality. So while the test might indicate a negative density range of 1.25, the resulting development will produce a negative density range of 1.05 for statistically normal scene matching the negative's density range to a grade two paper's LER.

We've already discussed the meter. It actually doesn't see Reflectance. It reads Luminance. What it wants to do is make an exposure of 8/ISO at the film plane. When the 2.20 luminance range has a diffused highlight at 100% Reflectance under Sunny 16 conditions, the luminance at the metered exposure point will have an effective Reflectance of 12%. The Zone System calling it 12 or 18 isn't going to make a difference at the film plane.