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Critical Thinking 2 - Normal Negative Density Range - ZS vs Tone Reproduction


This is the part that throws the gears in my head. Somehow, my brain won't wrap around this one. Sorry, it sticks in my craw every time you say it---I think it is purely a visual thing because I'm unable to relate it to my own curves.
 
The film's characteristic curve is contacted. You need to find a way to project what the effects of flare would do on it. Take a look at one of the four quad examples that have normal exposure and flare. The straight line in Quad 1 is an reference curve with no flare. The flare curve shows affects flare has on the distribution of the illuminance range. Both curves have the same exposure. As you can see, the non flare curve's shadows fall further down into the toe of the film curve. Flare brings the exposure up one stop.

Another way to look at it is the shadows on both camera image curves are four stops down from the metered exposure, but the flare curve is actually four stops down minus one stop less because of flare, so it is effectively only three stops down. When working with just the film curve you have to find a way to factor that in. I guess what I'm saying is the film's curve is showing the effects from the camera image curve without showing the camera image curve. With the ISO speed point, average flare is automatically factored into the film speed. There is a lot of theory behind the standards.

Chuck, perhaps you are having trouble getting it because I'm not explaining it properly. But I'm working on it.

What's great about the four quadrant reproduction curve is that it is visual. You can see how everything interacts. Working with it as I am, I've found the two quadrants that provide the most information aren't the film or paper quads.
 
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Stephen Benskin said:
Chuck, perhaps you are having trouble getting it because I'm not explaining it properly. But I'm working on it.
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I'm sure I am my own stumbling block.

Here's an interesting post I stumbled across last night from Phil Davis (January 2003) on the subject of flare factors---he was being asked by someone in his forum about flare factors:

"I didn't really intend to make flare testing all that big a deal. The procedure I outlined in the book is a way to become aware of the general effects of flare on image quality, and the results are interesting, but it's far from a definitive calibration procedure. I certainly don't recommend testing individual lenses for flare effect because I'd consider that an exercise in busy-work. There are far too many variables affecting flare to make any such calibration reliable, and as individual users (not trained in optics and lacking proper measurement equipment) we have no way to identify the causes of flare or measure their effects.

I suppose this sounds contradictory, given the apparent emphasis I've placed of "objective testing" procedures, but realistically we have to recognize that there are some things we can't measure and can't control. Rather than pretending that we can, and probably coming up with faulty data, I think it's better to look for trends of behavior and try to provide average compensation for effects we know are present. We do know that every lens-formed image will be affected by SOME flare and we know that modern coated lenses keep internal reflections (and potential flare effect) to a minimum. We also know that subject and light conditions can influence flare, but we can only guess how serious the effects will be. We do know that the general effect of flare is to increase B+F density and reduce image contrast (it also affects image gradation but we can't do anything about that during film exposure).

What we CAN do is decide on compensation that will tend to restore image contrast, and try to relate that compensation to subject range, because, as a rule, contrasty subjects are more flare-prone than are flat subjects. This is what we've tried to do in the ExpoDev program by providing an optional value of "flare compensation." Basically all this does is increase development in an attempt to restore contrast. We've settled on "0.02" as a suitable number for general use, but left it in an edit field so the user can change it. Increasing that factor will increase image contrast; decreasing it lowers contrast. Setting it to zero gives you exposure/development data that include no compensation at all and would be applicable for contact printing.

I have no idea what the maximum flare effect might be in pictorial photography, but I suppose it might result from fogging the lens and pointing it directly at the sun. Under more realistic conditions I know of no better way to cope with flare than to take pains to keep the lens surfaces clean, use an effective lens shade, try to avoid including light sources in the picture, and provide some development increase for subjects that seem likely to be unusually conducive to flare.

Practically speaking we have to keep things in perspective. As BTZSers are probably tired of hearing me saying, "some things are worth worrying about and some are not; the trick is to figure out which are which." I'd put individual lens flare differences in that last category."

--Phil Davis

I thought it was an interesting post.
 
Interesting test results. Despite all my efforts to do this independently my own way...

I have placed exactly 6 2/3 stops of subject (sensitometer, no-flare developed to ASA gradient) on the useful scale range of my paper.
 
Bill,

Would you mind explaining the test in more detail?

Chuck,

I completely agree with Davis. Flare is difficult to test for and it's not worth doing a flare test for every lens one owns. That's why I recommend using statistically average flare.

The way Davis explains his program's handling of flare compensation is one the reasons why I decided to write my own plotting program. His approach is pragmatic and will produce good results. I wanted something that could do theory with.
 
I have to fix a few things (clean the enlarger lens) and re-run the development time tests now that I have gotten more consistent at developing.

For my test I used the sensitometer to expose a sheet of TMY-2. I developed the film and read on the densitometer that I was close to ASA gradient so I put this negative in my enlarger and made a print of it.

Knowing which sensitometer step made the patches on the print, I graphed (with x-axis reversed) Log MCS and resulting print density.

Now all I need to do is convert my spotmeter readings to MCS. Then I need to figure out what other factors interfere with predictions.
 
I've attached something I did in Mathcad. It shows film plane exposure H from the metered exposure point down into the shadows in non flare and flare conditions. With flare you achieve the same exposure from a RD one stop further down into the shadows. Assuming these conditions, you can use the easier to control and interpret non flare conditions to calculate the film speed.
 

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This comment come years after the original post and, believe me, I'm wouldn't have been (and still am not) qualified to participate in this kinda scientific discussion anyway. That said, after reading most of this thread — to reveal what little I think I do understand about the subject — I've always described the Zone System as "bubble gum sensitometry" and I don't think that Ansel (or Fred Archer) ever had the pretension of it being as accurate as "real" sensitometry in the first place; it was, after all, originally conceived in large part [at Art Center College of Design] to help non-photographers (not only photography students, but art and design students who were not necessarily technically apt!) apply a level of technique that could help them achieve professional results and/or give them an artistic approach (predictability and therefore visualisation). Even though the Zone System, which may be, at its best and compared to full-on sensitometry, inexact and far from being as precise. . .it's a working method that's long been proven to be able to yield exceptional results even if we print a negative [whose density range, applying strictly sensitometric parameters, calls for a grade 2 paper].. on grade 1. Just let it drown in selenium toner for a while, I guess!
 
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@christophern I’d be interested to hear a story how you “used” the Zone System, maybe in school or on your own.

Did it get you the results you wanted? Did you hate the class? Did you like the instructor? Did you learn anything else in the class that you use every day? Or maybe once in a while?

I was a fly on the wall as my brother-in-law Chris pulled out a print he had made in school while a student of Henry Gilpin in Monterey. He was talking (at a party at his ranch) with Cara Weston who had the same class and was incessantly grilled because he expected more from her because of her family. My brother-in-law was proud of his photo which earned him bragging rights of an “A++”.
 
The premise for the zone system is false. The fact is that all negatives should be processed the same. Altering the contrast of the negative to accommodate different subject brightness ranges distorts the mid-tones, and those are the most important of all. Forget the zone system.

Read this:

 
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(From: Negative Making for Professional Photographers, Eastman Kodak, 1956.):
“As the portrait photographers have their adage, so also do the commercial photographers who say,
“Expose for the shadows and develop for the highlights.” Is this sound advice? First, let us
examine this statement more closely. Admittedly, adequate exposure is desirable to record the
important shadow tones. But to “develop for the highlights” implies that the time of development,
or in other words, the gamma, should be varied in accordance with the brightness range of the
scene. The idea is, of course, to prevent over-development of highlights, so the scale of tones can
be kept within that which photographic paper can render. Thus, should a negative of a short scale
subject, such as an average building exterior taken on an overcast day, be developed to a higher
gamma than a negative of the same scene taken in brilliant sunlight? The answer is generally no;
both negatives should be developed alike. This is probably contrary to the practice which some
professional photographers advocate. The reasoning for this answer follows: Although photographers
speak of “important highlights” and “important shadows,” for the most part it is actually the
middle tones which are most important of all. Middle tones are, of course, the range of grays
between highlights and shadows. Stated differently, middle tones of a negative or print are those
densities which are not associated with toe or shoulder areas of the characteristic curve.
It has been found through a series of comprehensive tests that for the great majority of scenes
the middle tones should be reproduced at a gradient of 1.0 on a tone reproduction curve. This
curve is a plot of densities in the print versus the logarithms of the luminances or
“brightnesses” of corresponding areas in the scene. A gradient of 1.0 means that if there is a 10
percent difference between two tones in the scene, then these same tones should be reproduced with
a 10 percent difference in the print. Generally speaking, the middle tones should be reproduced
with a gradient of 1.0, even if this can be done only at a sacrifice of gradient in the highlights
and shadows.
In other words, the majority of people want the middle tones of the print to reproduce most
original subjects as closely as possible, regardless of the lighting conditions that prevailed
when the pictures were taken. To do this, all negatives should be developed to the same contrast
or gamma for the same printing conditions and paper grade.
There are exceptions, of course. The “majority” of outdoor subjects in the tests mentioned
previously included about 85 percent of picture-taking situations, such as portraits, landscapes,
and architectural pictures taken in sunlight, in shade, and on overcast days. The remaining 15
percent of the scenes had, for the most part, large and very deep shadow areas which comprised an
important part of the subject. It was these latter scenes which the majority of observers thought
were best printed on a paper one grade softer than normal. Thus, even for subjects with a long
scale of brightnesses, it was found satisfactory to develop the negative as though for a normal
scene and to let the range of paper grades compensate for the unusual nature of the subject. In
other words, the varying lighting conditions may demand the use of a paper grade other than No.2
for best results.
However, unusual subjects in which heavy shadows may either be present or actually predominate the
scene are usually treated differently by professional photographers than they are by amateur
photographers. The professional uses fill-in flash illumination, whereas the amateur does them
without the benefit of supplementary illumination. The flash converts an “unusual” subject into a
“normal” subject, and as such requires a normal negative development and will print on a normal
grade of paper.
The degree of negative development for some subjects naturally depends on the photographer’s
“artistic intent.” For example, suppose he were to photograph a sailboat at anchor during foggy
weather. If it is thought that the fog lends a desirable pictorial effect to the scene, then it
can be reproduced as the eye saw it with a normal negative development and a print on No.2 grade
paper. If, on the other hand, a clear record picture of the boat was the photographer’s object,
and the exposure could be made only under a fog condition, then the negative should receive more
than normal development to compensate for the contrast-reducing action of the fog particles. In
this case, over-development of the negative is desirable only if a print from a normally developed
negative on No.4 paper grade would contain insufficient contrast. Accordingly, in view of the
desirability of reproducing most scenes with a gradient of 1.0, and because of the wide control
over contrast possible with various paper grades, it is highly advisable for the professional
photographer to develop the great majority of his negatives to the same gamma.
A sensible approach to planning a standard photographic technique, including the degree of
negative development, is to strive for a negative that will print best on a normal grade of paper.
Although there is no necessity to confine oneself to anyone gamma if several paper grades are
available, it is only logical to aim for No.2 paper. If this is done successfully, the printing
problem is simplified by using one grade of paper for most negatives. At the same time, the
photographer is protected on both sides of normal by papers with greater or less contrast
capacity, should an underdeveloped or overdeveloped negative accidentally result.
Kodak processing recommendations for film are generally based on the use of diffusion-type
enlargers, or on contact printing which results in prints of approximately the same contrast,
everything else being equal. Obviously, these same processing recommendations should be modified
by a reduction of 15 to 20 percent in gamma to suit condenser-type enlargers if prints of the same
contrast are to be obtained.
Individual preferences are shown in a survey made of several individual newspapers and the
principal news photo services. The results showed that films were developed to gammas ranging from
0.62 to 1.18, with an average of 0.85; that Kodak Developer DK-60a was the most popular of the
developers, although a number of others were used; and that developing times ranged all the way
from 4 ½ to 8 minutes. The photographers who preferred the lower range of gammas used condenser
enlargers. The ones who developed films in the intermediate range used tungsten-source, diffusion
enlargers, and those using the highest gammas employed mercury-vapor enlargers. In a similar
manner, commercial and, to a lesser extent, portrait photographers also modify the basic
development recommendations according to individual conditions.”
 
The vast majority of film is developed to a normal contrast. But it’s not the old normal.

People today do not develop to “gammas ranging from 0.62 to 1.18, with an average of 0.85.”

I develop to contrast index 0.62 but I consider myself by the exception not the norm. I believe the norm is closer to 0.55 but if you have a different idea let me know. I just know people reduced the contrast significantly.

People today read the data sheet or ask here or use the Massive Dev chart and take the time for their film and developer combination, without knowing what contrast they might achieve.

The Zone System, for all its faults, still teaches how to decide what contrast to aim for.

And nobody would suffer harm by exposing according to test results and developing to Zone System N which they find bu testing.
 
The light source of the enlarger will make a difference too. Negatives developed for a condenser enlarger are usually developed for a much shorter time than those required for a cold cathode enlarger. Most modern enlargers designed for colour papers and variable contrast black and white prints fit somewhere in between the two.
 

Hello Bill,

I'm wondering if your question was addressed to me, as I don't understand some of it, but here's a partial answer, just in case .. and forgive me if I'm answering in someone else's place!:

I cannot say that I have ever really "used" the Zone System (I mean, in its entirety, as outlined by Saint Ansel and his many apostles) with a possible exception — if memory serves — of a short period in the early 1970s when I was befriended by the incredible Al Weber, who became a mentor. That is not to say that I do not apply many of its principles and concepts, but I do not consider applying ZS metering techniques (without having done the prerequisite film developing and printing tests), and then applying guessed-at development changes as a full on "system" of any kind, but, rather —with repeated and noted use — a disciplined empirical approach [which of course has its merits and which I sometimes jokingly call, The KNOW* system . . . deliberately rhyming with, "no"].

Did I get the results I wanted? Yes, often.

Cheers,

Chris
 

Well, the first thing to do is the establish what a "normal" grade of paper is, then test various film developing times so that the negatives print right on that. My "normal" is Ilford Galerie grade 3. Grade 3 is recommended for 35mm film.

My trials showed that the new Ilford Multigrade V using the filtration that Ilford recommends for grade 3 has more contrast than grade 3 Ilford Ilfobrom Galerie. I found, then, that I had to use a different filtration to match the contrast of Galerie Grade 3. It is less than called for here:


Also, different taking lenses and enlarging lenses will affect the contrast. (For instance, my latest copy of the Leica 21mm f/4 Super-Angulon-R is multi-coated, and the effect is noticeable.) For that reason, one might have to make slight adjustments in the "normal" filtration when using VC papers.

I do not follow, use, or accept any principles of the zone system. It is unnecessary and counter-productive. My work method is simple. Film engineers have designed films so that the vast majority of scenes will print well without adjusting film development, and any slight changes in contrast can be made in the printing stage, but these should be infrequent and minor.
 
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christophern said:
Hello Bill,

I'm wondering if your question was addressed to me

a short period in the early 1970s when I was befriended by the incredible Al Weber, who became a mentor.

..,

Did I get the results I wanted? Yes, often.

Cheers,

Chris
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Yes I was hoping for a story of a mentor, I’d like to hear more of your time with Al Weber, even if it goes off the rails of this thread…
 

Sounds like you’re dialed in to normal for your work.

I’m often critical of certain technical errata surrounding Zone System, but wholeheartedly accept Zones, tone placement (and falls), N, N+ and N- development notation.

In photography schools, Zone System is how sensitometry was taught.

I got to learn sensitometry in high school print shop where Mr. Ford would call you a pinhead if you didn’t put a Stouffer scale on the copyboard. In college there were further courses where we learned to plot D-LogE curves.

Marty Sanders my boss and Pete Perez my foreman in Porterville had a lot in common with Mr. Ford. They wouldn’t even talk with you about a problem if the film didn’t have a Stouffer scale on it.

I got to be pretty good with densitometers in those days.
 

What should the negative density range be for enlarging on grade 3 papers if using 35mm films?
 
Have you guys ever thought about looking at the picture?
 
cliveh said:
Have you guys ever thought about looking at the picture?
Click to expand...

This is why Photrio is divided into various sub-forums - to allow members to "focus" on all sorts of different things
 
Stephen Benskin said:
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That's a bigger difference than I would have thought. No wonder my overdeveloped negatives (manufacturers' development times) printed so much better when I went from a Magnifax condenser enlarger to a cold light head in the 1970s. Would I be right in thinking that in the table above that the Condenser Enlarger cited is a pure condenser enlarger not one softened by a matt globe (if that's the term).
 
Keith Tapscott. said:
What should the negative density range be for enlarging on grade 3 papers if using 35mm films?
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Because sharpness is greater and graininess is less than giving more development and using softer paper. From: Kodak Films (7th edition):


"Graininess. When a negative is viewed at a sufficiently high magnification, it is seen to possess a grainy or granular structure. This impression of nonuniformity in the image is called graininess. It is caused by the irregular distribution of the silver grains, rather than by the individual grains themselves which are visible only under magnifications much greater than are used in making ordinary enlargements.

For emulsions of a given general type, graininess tends to increase with the emulsion speed. When development is carried to the same gradient, the common developers of normal and high activity (e.g., Kodak Developers DK-50, D-72, and Dektol) produce approximately equal graininess with a given film. Some fine-grain developers (e.g., Kodak Developers DK-20 and Microdol) produce noticeably less graininess but at the expense of some loss of speed. Graininess of the print increases with the density of the negative, so overexposure or overdevelopment of the latter should be avoided.

The graininess of both negatives and prints increases with increasing gradient of the material on which they are made. When the gradient of the negative material is low, prints are normally made on a paper which has a high gradient and vice versa, so what may be gained by holding one gradient down would be largely lost by the high gradient of the other. It is usually true, however, that a low gradient in the negative material and a correspondingly high gradient in the paper is more favorable than the alternative combination."
 
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Thanks. I have an old magazine somewhere that says that 35mm films should be exposed and processed to be printed on grade 3 as standard rather than the usually recommended grade 2.

It makes sense because of the higher magnification required for the small negatives. It also covers optimum F/stops to squeeze maximum image quality.
 
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