Photo Engineer said:Sandy, that is what I have been saying. The micro-contrast has nothing to do with the macro-contrast. It seems that you agree with me after all!
I'm also interested to see all of the discussion about the zone system. The zone system is merely another way of expressing an H&D (sensitometric or characteristic) curve. And this curve, whether in the zone system or as a measure of density vs LogE is the way you measure contrast on both a macro and micro scale.
Perhaps you should re-read my messages as well.
PE
noseoil said:Kodak is just doing a CYA. They would never admit that a "neophyte" like Sandy might have come up with a superior actinic developer for use with many different films and processes. Kodak is in business to sell Kodak. Sandy is in "business" to improve photographic quality and contribute to the community of photographers, not to toot his own horn (in my estimation, only). tim
P.S. Sandy, sorry for the editorial comments about your work. I don't know of too many people who are actively trying to improve photography for photography's sake, do it selflessly and then share the results so graciously. I tip my stout to thee, sir.
I don't know how you came up with this assessment of what I did. You certainly did not read the article I wrote for Photo Techniques.Photo Engineer said:Sandy, yes, I stand corrected on the matter of your agreeing/disagreeing. Sorry.
You are right that the human eye can judge which picture is sharper, but the human eye and brain can sometimes be fooled as to their judgment. One example is stated in my quote of Gainers post above. He tested macro contrast and changed development to match those values, apparently before comparing prints, and this is what can cause a person to step into a situation that leads down the wrong path. We may never know what conditions were between those extremes of identical macro contrast. I think that is to the point here. The two conditions with unmatched macro contrast might have revealed identical micro contrast and a useful position to be in for printing with a potentially longer tone scale with a sharper image. The prints were apparently never made or compared, as the macro contrasts were not equal. Instead, the process was changed until the macro contrasts matched. Then the comparison was apparently made. That is my point here.
PE
It appears that there are many other articles you have not read, if you are limiting yourself to those you happen to have on hand.Photo Engineer said:Patrick, the response to a step input, the characteristic curve, the H&D curve and the zone system are all different names for the same thing, and that is the response in density of a film or paper to a stepped exposure in increments of 0.15 or 0.3 log E. They are plotted or sensed by the eye as a change in density vs exposure.
These exposures may be macro or greater than 1000 microns in width or micro which is usually taken as 1000 microns and smaller in width. Both types may be plotted as density vs log E yielding a measure of macro and micro contrast or they may be interpreted by the eye as the tone scale of the photograph.
The fourier transfer of the micro densitometry over all line widths will give MTF. In a way, this is a numeric representation of sharpness.
You said "I did some characteristic curves with and without agitation. Since the purpose was to find the effect of no agitation vs agitation, I used the same developers in both cases. I found that the developing times had to be 40% longer to get the same contrast index for each of two developers. In neither case was there any significant difference in shape of the curve."
You made no comment about sharpness and that was exactly my point. We know you changed development to match macro contrast, but know nothing about the print results at any of the conditions.
Now surely you know that not all of us have read your article and therefore the comments you make directing us to it are not useful here. Your comments must be taken within the context of this thread just as mine must be. Since the comments above relate to sharpness and stand or semi-stand development, then that is the context we have to work with. We have no information on how any process condition affected sharpness or micro contrast.
That is the only point I wanted to make.
PE
fhovie said:I understand "accutance" I wonder if the word accutance has been usurped by "micro contrast" I used to use PMK in a motorized drum. I was happy with the results but did wish I had more accutance. I then started filling the tank all the way and using normal inversion development. The accutance (apperent sharpness/edge effects) improved. Then I tried partial stand development, there was a slight increase in accutance and an increase in film speed. Both are benefits.
These benefits are not realized with all developers. I have not observed increased accutance in developers that use TEA. TEA seems to be great with PH and blocking oxidation but it is not any kind of silver solvent. The edge effects seem to require the action of some kind of silver solvent to move silver to the edge for a build up. So XTOL gives pretty good accutance and very fine grain. PC TEA and Pyro 510 do not seem to help accutance much at all no matter what I do. They do not erode accutance like Microdol or D76 or D23. So sharpness is not degraded - but no increase in sharpness due to enhanced accutance. So I have wandered down the path of fine grain/accutance tradeoffs and I keep coming back to PyrocatHD. I will probably try Hypercat before long. Although I like the convenience of the TEA developers - I will likely use up what I have and then relegate TEA to the printing tray only - where it is extremely wonderful stuff!
jdef said:Sandy,
when you introduced your Rollo-TEA formula, which contains both phenidone and ascorbic acid, you claimed for it sharpness similar to PMK or Pyrocat HD. Why the inconsistency?
Jay
sanking said:I can not provide any useful information on any of the specific developers you mention other than Pyrocat-HD. However, in developing the formula for PMK Gordon Hutchings experimented with a number of different reducers in superadditive combination with pyrogallol, and came to the conclusion that phenidione and ascorbic acid decrease edge effects as their concentrations are increased. On p. 55 of the Book of Pyro he writes: "while phenidone and ascorbic acid are more super additive with pyro than metol, this research [described as "estensive tests including microscopic analysis"] shows that phenidone, and particulary ascorbic acid, decrease edge effects . . . "
As you perhaps know, much of my own preliminary testing of Pyrocat-HD was done with pyrocatechin + metol, although I later settled on pyrocatechin + phenidone for the standard formula. However, and I have made this observation many times, with normal agitation patterns the metol variant of Pyrocat-HD is sharper than the phenidone version. In adding ascorbic acid to the mix, i.e. pyrocatechin + phenidone + ascorbic, I have observed what appears to be a further slight decrease in sharpness. The solution is much more energetic but the down side of a slight decrease in sharpness is the main reason I don't recommend the addition of ascorbic acid to Pyrocat-HD except in cases where one needs an especially energetic developer.
Sandy
jdef said:Sandy,
if I read more into your post than was intended, I appologize, but I do find it puzzling. It's not as if you have no personal experience with TEA-based developers containing pyrogallol, ascorbic acid and phenidone. You recently wrote me that you were preparing an article on your Rollo-TEA formula for publication , so why would you defer to Hutchings if you've done your own research that is more relevant to the developers in question? From a reader's perspective, it seems that you are suggesting, through your citation of Hutchings, and comments about the differences in Pyrocat HD and Pyrocat+, that you believe that ascorbic acid and phenidone degrade sharpness in pyrogallol and catechol-based developers. That would appear to contradict your claim for Rollo-TEA of sharpness similar to PMK and Pyrocat HD. If I've made unreasonable inferences, I hope you'll clarify your position.
Jay
Jorge said:Since you are interested in semi stand developing, wouldnt it stand to reason that using the Metol variant with Pyrocat HD would be of greater benefit when using semi stand since it produces sharper negatives?
Which brings me to the question, have you done any testing with resolution charts? I am just curious, but I cant help to think that every time people say their negatives are sharper I always want to know sharper in relation to what?
A resolution chart, another negative, what?
Jorge said:Since you are interested in semi stand developing, wouldnt it stand to reason that using the Metol variant with Pyrocat HD would be of greater benefit when using semi stand since it produces sharper negatives?
Which brings me to the question, have you done any testing with resolution charts? I am just curious, but I cant help to think that every time people say their negatives are sharper I always want to know sharper in relation to what?
A resolution chart, another negative, what?
jdef said:Hi Sandy.
Thanks for the clarification. I'm glad I'm not imagining things, and there is indeed an inconsitency between your initial reporting on Rollo-TEA, in which you claimed it was as sharp as PMK and Pyrocat HD and your present reporting. As this thread well illustrates, quantitative sharpness determinations are difficult to make, and most of us rely on our own qualitative analyses. For my part, I find both 510-Pyro and Hypercat to produce sharper negs than Pyrocat HD, given a similar agitation scheme. I have a theory as to why this might be true, but no means to quantify my results. There are a few variations on my 510-pyro formula that I've been meaning to test, but the truth is that it works so well as-is, I haven't been highly motivated to run the tests. I have, instead been working on a coffee-based developer for those who want to try a staining developer, but aren't comfortable with the relatively toxic pyrogallol or catechol that are used in most staining developers. This developer is also very sharp, but has many disadvantages compared to more traditional staining developers.
Jay
Go find a good text book on system analysis and learn what is meant in the system analysis language by Step Input, Unit Impulse, Modulation Transfer Function, Linear System and other terms. A linear relationship between the subjective perception of sharpness and any physically measurable character of an image has no bearing on whether, given a set of H&D curves, you can determine the Modulation Transfer Function. Visual perception itself is logarithmic with thresholds and other deviations from linearity. Sharpness is not directly related to resolution, although it is true the the greater the resolution, the less need for artificial sharpness from adjacency effects. Go to an art gallery and see how many works recognized as great paintings have edge effects.Photo Engineer said:According to Mees, "The property of a photographic material that leads to pictures having good screen definition is commonly referred to as sharpness". However, he admits that this is a subjective concept. Therefore the edge effect measurement (knife edge exposure) is now applied to the term sharpness in the quantitative measure. However, maximum gradient (maximum 'contrast') and average gradiant (average 'contrast') do not correlate with percieved sharpness either.
The subjective or percieved sharpness is termed acutance and is the average of gradiants obtained from these knife edge exposures.
It depends on this average and the density scale of the film.
In all cases, there is apparently a linear relationship between acutance and sharpness as shown by many researchers, but one is quantitative and the other is qualitative. However, it cannot be derived from the characteristic curve of the film.
The ability of a film to record fine detail is called resolving power. This is a third way of looking at this and it uses the slit exposures.
All of these are bound up together.
Oh, and for Sandy King, Mees publishes plots of resolving power vs gamma for 3 developers.
PE
jdef said:Sandy,
there's no need to get sarcastic. I quote you because I find that paraphrasing a person often leads to unecessary confusion and the introduction of bias.
Jay
noseoil said:Pardon me while I retreat to the bathroom to stroke my own ego.
.
P.S. Group grope everyone.
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