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

[Stephen Benskin]

No matter how much you think you understand something, any feelings of complacency are shattered when you have to explain it to someone else. They say no one learns more in a classroom than the teacher. And that pretty much sums it up when I was teaching a class and the lesson was on the Zone System. Like many people, I started with the Zone System, but soon I moved onto more scientific versions of sensitometry and tone reproduction.

When it came time to teach, I had to finally face certain concepts that didn’t seem to match up between what I learn about sensitometry and what the Zone System was explaining. One of these dilemmas is on how to define a normal negative. The basic idea is to process the negative so that the negative density range will fit onto the paper’s log exposure range. While sensitometry uses the method that is described in Chuck’s thread “Testing for Relative ISO Range Numbers”, the Zone System has a set of density aim values for the negative to fit onto a grade 2 paper.

According to sensitometric and tone reproduction theory, a paper with an LER of 1.05 is considered a grade 2 paper; therefore, a negative with a density range of 1.05 should fit nicely onto the paper.

According to Zone System theory, the negative density range for a grade 2 paper is 1.25 (1.35 – 0.10). Sensitometric theory says that is the range for a grade 1 paper and not a grade 2 paper.

Obviously one has to be wrong. Since a negative with a density range of 1.25 will be too contrasty for a LER 1.05 grade 2 paper, it must be the Zone System’s approach that is incorrect. Except that in practice, both methods seem to work. Thus the dilemma.

Some people don’t seem to have problems not questioning such differences. Personally, I had blown off the Zone System values as coming from a less precise, less sophisticated method. That is until I had to explain it and why it still worked. I had to ask myself how two seemingly dissimilar methods that had different stated aim values could produce similar results.

There’s a good reason for it and an important lesson that should be kept in mind by everyone when testing.

[Hikari]

Are you also taking into account that there is a loss of contrast in the printing process. The Zone System number may just be compensating for that. I guess if you were making contact prints with a point source, then the density ranges would not match up.

[Stephen Benskin]

What you are referring to is the Callier Coefficient. While it's not stated in the post, the default is generally to diffusion enlargers which are the numbers I used.

Also, won't any influence in the printing process have the same affect on the negatives produced by either method?

[CPorter]

According to Zone System theory, the negative density range for a grade 2 paper is 1.25 (1.35 – 0.10). Sensitometric theory says that is the range for a grade 1 paper and not a grade 2 paper.

Obviously one has to be wrong...........

Stephen,

I have made such observations myself on this seemingly glaring discrepancy. It's my opinion, but I don't think it can be explained away in mathematical terms---I believe it is a matter of "wiggle room" for aesthetic possibilities, according to AA, as I see it. I'll use a quote that I think sums it up from the third book in his series, The Print:

"A low-contrast negative combined with a high-contrast paper will yield a print in which some compression of light values occurs, and the shadow values may be darker than anticipated because of the effect of the paper-curve "shoulder." Less difficulty occurs when printing a contrasty negative on a soft paper, but standardizing on a Grade 0 or 1 paper leaves us no softer choice for "emergency" requirements. It is therefore best to control the contrast scale of the negative as much as possible, and standardize on a Grade 2 or 3 enlarging paper."
--AA

The above is just something that I think hints at what you are getting at, but of course, I don't know for sure and I don't believe there is necessarily an oversight but it's obviously more than I can really expand upon.

I find these statements interesting as well from The Negative:

"The density values I prefer for diffusion enlargers have a range of about 1.2 (from Value I to Value VIII), which I have found to be optimum for printing on Grade 2 paper. However, the Grade 2 contrast varies among the different manufacturers, and the trend in recent years seems to favor a shorter exposure scale for the so-called normal papers; thus this optimum range must be subject to continual review and revision as required."
--AA

All I can say is that I use that same range in my ZS testing today and it seems to work quite well for me and so I don't question the mathematical alignment, so to speak, of my own results when my eyes, quite simply, like what they see, but I recognize the apparent discrepancy you are speaking about. It makes me wander if the ISO RN's have always been what they are as we understand them today. Meaning, has R105 (i.e., LER 1.05) always been the ISO standard for Grade 2? Perhaps the RN used to be higher for Grade 2, IDK.

[ic-racer]

PRACTICAL THINKING
Here is my take on it: It is moot, because who has an orifice on their densitometer small enough to measure the negative range anyway? Mine is 3mm but the optional 1mm opening could still allow 50 leaves and part of a tree...and that is on one of my 8x10 negatives. For 35mm that 3mm could easily encompas an entire automobile and part of the road, etc....


For me, measuring a negative for its density range is indicated in troubleshooting only. I woud not do it on a routine basis. Kind of like driving around with the OBDII monitor hooked to your car. You need it when troubleshooting, but for driving to work every day, its not needed.

[Maris]

I try to produce negatives that have a density range greater (just!) than my target paper grade can record.

The dense parts will correspond to paper-white areas that still read right; specular highlights for example. The thin parts of the negative I consign to maximum paper black; twigs against the sky, gaps in rocks, for example.

Apart from aesthetic considerations small patches (say 2% of the picture area) of pure white and pure black calibrate the eye. Without them a viewer can't be sure if they are looking at a light photograph in a dim room or a dark photograph in a bright room.

[Stephen Benskin]

PRACTICAL THINKING
Here is my take on it: It is moot, because who has an orifice on their densitometer small enough to measure the negative range anyway?

I know it's fun to be snarky, but I believe you missed the point. It's about testing and defining testing parameters. You know, sensitometry, step tablets, matching the negative to the paper, what is "Normal"? Then you apply it in real world shooting conditions.

Chuck is doing the right thing with his paper testing. The aim negative density range is determined by the paper's LER. And that's the center of the puzzle. Two testing methods that produce similar to identical results on the same grade of paper yet the aim negative density ranges are different.

[ic-racer]

matching the negative to the paper,

Actually its all reasonable, but not practical to do. In 30 years I have come down that path many times. Exactly how are you going to measure the negative? You need to know the range of your negative to match to the paper, so you have to measure it by trial and error zeroing in on the highest and lowest areas.
One way to do this is that you can project it and measure the densities with a spot-baseboard meter (Nicholas Lindan method). But this is really my question to you guys (that want to measure the negative) how do you do it, I'm curious? My 'standard' densitometer has too big of an orifice.

What I do to rapidly measure the entire negative area for even the tiny itty-bitty highest and lowest density areas is to project the entire negative onto a piece of MG paper. By adjusting exposure time and contrast filtration I can precisely determine the point where the entire range of important negative values fits on the paper. The cool thing about this method is that when you are done you can frame it.

[Stephen Benskin]

I have made such observations myself on this seemingly glaring discrepancy. It's my opinion, but I don't think it can be explained away in mathematical terms---I believe it is a matter of "wiggle room" for aesthetic possibilities, according to AA, as I see it. .

I agree that personal taste plays a roll in determining what type of negative an individual desires. But wiggle room or personal preference isn't an issue in this situation as the two different test methods described above produce almost identical results.

I have to disagree about the math though. As the maximum density for the determination of the LER is 90% of the paper's D-Max, that leaves 10% of the paper's density range that some might like to work with. Also the matching of the negative to the print doesn't guarantee optimum quality. The subject matter, tones, and tonal distribution all play a part. In addition, there's a preference to print with a harder paper with a flat scene and a softer paper with a contrasty scene than what is would be normally indicated by simply matching the materials. And that's all math.

The question you need to be asking yourself has to do with the method of testing as the results appear to be similar. Since the results are similar, the answer has to lies somewhere within the process. Work backwards from the paper's LER. We know the paper's LER is the same as the negative's density range. What are the factors that will produce a negative with the desired negative density range?

[Stephen Benskin]

Yes, exactly how are you going to do that? You need to know the range of your negative to match to the paper. You can project it and measure the densities with a spot-baseboard meter (Nicholas Lindan method). But this is really my question to you guys (that want to measure the negative) how do you do it, I'm curious? My 'standard' densitometer has too big of an orifice.

You're just being blocked and are fixated on measuring the pictorial negative. The testing is done with a step tablet. Once you've determined the contrast index it's all just a matter of input/output.

Although the difficulty of reading the densities off a pictorial negative is part of the answer to the dilemma.