The tests are very hard to evaluate not knowing enough about the test equipment and other factors in the entire experiment. I would guess that there is no significant difference in many cases to justify certain preconceived notions. But then these are self evident in the data.
Kodak probably used D76 straight with Nitrogen burst agitation. The agitation at the start would be accompanied by hand agitation at the start to dislodge any bubbles. Otherwise, the agitation would follow that in the EK guidelines for time and quantity. The use of gas burst allows an exact setting for time, duration and pressure.
Indeed. I was torn on how much information to put in this summary. Henry is quite thorough in his detailed descriptions of the equipment, procedures (including comparisons to those of Kodak and others), and statistics (he was an analytical chemist after all), but a description of the microdensitometry alone would require a few pages and to detail the experimental methods properly I'd have essentially had to recopy tens of pages.
One thing which comes up repeatedly - findings essentially in agreement with Kodak. It is important to note he did not approach the excercise with the intention of proving Kodak or Ilford or Agfa wrong. In fact it would be surprising if his results differed wildly from those of reputable scientists and were in conflict with good theory. What he wanted to do was test the claims and assertions made by other people in books, magazines, articles and such. In general throughout the book he's quite good about comparing his findings with those of Kodak and other researchers, and then using all this to test the validity of statements made by others.
It is a book about applying proper scientific method to darkroom photography, since unfortunately this is almost never done by the people who often speak loudest. Where the book is less successful is the theory. The data can often show a claim to be true or false, but explaining why is another matter. That is not the primary focus of the book and Henry freely admits when he is unable to explain why something is the way it is. This is why I find the first half of the book about printing controls "better" than the stuff about film and developers. When it comes to printing it is easier to test the validity of many things that are said. When it comes to film processing on the other hand, things can get very complicated from a theoretical perspective. I think I would challenge a few of his interpretations of the data.
There are also still a couple of things I don't fully understand about his use of the acutance formula. This is also something I'm a little unclear on in the Altman/Henn study. The formula is still bothering me. It is assumed to NOT take edge effects into account, but then there's that Dmax-Dmin part of the equation... It's like "half pregnant".
A shame he is not around. While it isn't perfect, I think many people could learn a lot from his book. I wish I could carry on that type of work.
IMO you have done an interesting job to summarize the special case where the apparent sharpness is not affected by adjacency effects, the "old theory".
If you search for "sharpness developer way beyond monochrome" it brings up the book of Lambrecht and Woodhouse ,they include these effects by using MTF50 and that is IMO a good way to do it.
Michael R 1974,
You are bringing us this research well distilled with a clear concise explanation. What more can we ask?
Originally Posted by Alan Johnson
The general conclusion I keep coming to based on all this, Perrin, Altman etc. and descriptions/photographs of the formation of image silver during development in Haist's book, is that barring extreme situations, adjacency effects and graininess are the primary characteristics people are observing (consciously or unconsciously) when they describe a particular developer as "sharp" relative to some other developer. The typical comparison is between high pH, low sulfite developers vs say D-76. So I would tend to argue when we talk generically about "edge sharpness" in the context of developers, we're speaking mostly about micro-contrast (and I think graininess plays an important role in the subjective impression of sharpness too), not acutance as traditionally defined.
Strictly speaking, there is not really any such thing as a sharp developed silver grain, and at that scale I simply can't accept that differences in the amount of sulfite grain etching per se (compare say D-76 1+1 to Rodinal) have any material impact on traditionally defined acutance.
It then follows that on balance we are generally (depending on the film) better off with plain old mildly solvent developers from the standpoint of image structure. It would seem even where acutance increases are observed with so-called high acutance formulas, a very disproportionate price is paid in granularity/graininess.
I'd still like to get everyone (including PE) in a room to discuss this one day where we can draw diagrams, look at the books, photomicrograph pictures, data etc. The ideas can be tricky to get across in forum format.
Originally Posted by Bill Burk
Will continue to do the best I can.
I would be happy to join you all, but I am not the expert someone like Mike Kriss is. I would do my best to explain what we did and what we observed. The data posted on the Kodak web site is basically from KRL or a similar division which just runs routine tests like those described. The results are posted with the scales adjusted for all products to match a generic or common format.
I am not surprised that others can test films and come up with data close or identical to what we got.
Ah - but you are still the expert on photochemistry and what is actually happening at small scales. Some of the mechanisms and proposed theory Haist talks about when it comes to the formation of image silver are fascinating. When I first read the book I realized my mental picture of what goes on at the microscopic level during development was quite flawed. I bet most people are in the same boat.
I'd probably have to get some of the rust out of my calculus before tackling Kriss's work. On the other hand perhaps we could still have an intelligent discussion about the theory without necessarily getting into the mathematics of image content. Not sure.
I still have a few more things to post to the thread here so we'll see how it goes.
Here's Crawley ,Amateur Photographer,March30 2002:
"In the 1950's, researchers found that although fine grained negatives could give higher resolving power,the overall sharpness and detail crispness of an image is better from a rather grainier negative.The reason is simply that the grainier negative image diffused less in the enlarger,so detail was crisp and main subject outlines sharper"
"The point was made that,subjectively,the enhanced overall impact of a sharp print image makes any increased grain insignificant-especially when viewed from a normal distance rather than close up with a magnifying glass".
Of course Beutler started this many years earlier,he wrote a book in German Meine Dunkelkammer Praxis (sp?), I never saw it.
Hi, I guess I've been AWOL from this thread, but in my defense I don't have anything directly useful to add. Although I've worked in photography my entire adult life, I've never had occasion nor need to study acutance. Not that it wouldn't have been fun, just no way to justify it from a business standpoint.
Regarding information from Michael Kriss, he authored the chapter on image structure in Theory of the Photographic Process, 4th edition (James). If you can find a copy, there are about 40 pages of dense reading. I don't see it as directly practical info, mostly it applies fairly advanced mathematical treatments to things such as spread funtions. If you're familiar with the convolution theorem and Fourier analysis, then you might breeze right through this, but it's mostly beyond me.