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  1. #71

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    Edge effects

    Hi Gadget:
    Interesting to see what your background is. My background is physics and chemistry ( applied in the forensic area). After my retirement I found the time to focus, more than before, on human perception. My neighbor (Bouman) was the director of a Simulation and Human Factors research lab at an US-Dutch Soesterberg airbase and the director of an equivalent lab at the University of Utrecht. They used to use MTF for their descriptions of phenomena. They say to use other methods today. They even got rid of their microdensitometers. However, I stick with the MTF approach because it is the common language in the photographic world when it comes to image quality.

    I fully agree that edge effects are only part of the story. The properties of lenses, and the rest of photographic procedure are playing an important role. And, do not forget the properties of the human eye. I am trying to write a text on the subject. At least, I am being asked to do that. It is a real challenge.
    You might think, that I am a theoretician testing assumptions. That is not the case. I am using the results and recommendations of other research groups on image quality. A German research group had a panel of 4.000 people, when it comes to sharpness! Then I make use of their recommendations in actual photography, and see if it works, using a (smaller) panel. It is very simple, I am a photographer, just using the recommendations of research groups on image quality.

    Jed

  2. #72

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    Quote Originally Posted by Tom Hoskinson View Post
    Jed, you are misrepresenting Hans Windisch. Nowhere does Windisch discuss deposited or redeposited silver.

    Here are two direct quotes from The Manual of
    Modern Photography by Hans Windisch, page 89, Pyrocatechol Compensating Developer (Windisch's formula).

    "Owing to the small amount of sodium sulfite used, the developer has a tanning effect, producing negatives of a brownish color."

    "Negatives developed with Pyrocatechol cannot be reduced or intensified as it tans the emulsion."


    The tanned and stained (polymerized) gelatin image produced by Windisch's Pyrocatechol Compensating Developer (and other tanning and staining developers) is very stable (DEMONSTRATED BY TEST - Haist, Neblette, et.al.).

    However, a silver image is also produced which can be bleached out. After bleaching, a very stable (polymerized), tanned and stained gelatin image remains. The tanned and stained gelatin image demonstrates good photographic printing density (DEMONSTRATED BY TEST - Haist, Neblette, et.al.).

    Hi Tom:
    I am not in the possesion of an english version of the book of Hans Windisch. Most of them are in German, and there are later versions in the Dutch language ( but they are modified by the translater too). In the book, I have, Windisch does mentione the tanning effect and that it cannot be reduced or intensified.

    And then I quote: 'the silver deposit is brownish', when I try to translate this accurately.

    I get the impression that there might be a change in the text in the translation process.

    I was trying to find the spot where Haist is quoting a reference. But was unable to find it. Would you be so kind to give the page in the book of Haist. The quotation can never be from German origin, because the Germans do not have a word like 'staining'. The Germans describe the phenomena they observe.

    Jed

  3. #73

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    Quote Originally Posted by sanking View Post
    I find your discussion of edge effects somewhat confusing. First, you appear to be saying that a developer such as your catechol HD developer that uses only one reducer does not give edge effects, but developers that contain more than one reducer give edge effects? If that is true, it is contrary to my understanding, which is that a single reducer devleoper is more likely to exhaust faster and create edge effects than a developer that contains two reducers.

    Second, I don't agree at all with the opinion that edge effects are not necessary or desirable in LF photography. In fact, I am of the opinion that edge effects are at least as desirable in LF negatives, if not more so, than in 35mm and roll film work. This opinion is not based on theory but on close inspection of contact prints made from LF and ULF negatives.

    Sandy King
    Whether you like edge effects or not is a matter of taste. Crawley made developers with a engraving-like appearance. However, for regular pictorial work, many people ( panels) do not like them.
    A single reducer developer, with suffucient developing agent, sufficient agitation etc. exhausts usually less than a developer with more agents (but this is very generalized speaking). The effect of an edge effect is, however, reflected in the MTF. Many of that has been published. I have given one reference (Nelson) in this thread already.

    Jed

  4. #74

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    Quote Originally Posted by Jed Freudenthal View Post
    Hi Tom:
    I am not in the possesion of an english version of the book of Hans Windisch. Most of them are in German, and there are later versions in the Dutch language ( but they are modified by the translater too). In the book, I have, Windisch does mentione the tanning effect and that it cannot be reduced or intensified.

    And then I quote: 'the silver deposit is brownish', when I try to translate this accurately.

    I get the impression that there might be a change in the text in the translation process.

    I was trying to find the spot where Haist is quoting a reference. But was unable to find it. Would you be so kind to give the page in the book of Haist. The quotation can never be from German origin, because the Germans do not have a word like 'staining'. The Germans describe the phenomena they observe.

    Jed
    Jed, this is what the 1957 English edition of Han's Windisch's book says: "Owing to the small amount of sodium sulfite used, the developer has a tanning effect, producing negatives of a brownish color."

    It appears that this English translation from the German Edition was approved by Windisch.

    In any case, IF the "brownish color" Windisch describes was caused by re-deposited silver (as is the case with Kodak's Microdol-X Developer), it should be removable by bleaching (with a ferricyanide bleach).

    When I bleach a film developed in Han's Windisch's catechol developer, a tanned, stained, brown image REMAINS - QED

    Regarding page references for Grant Haist's statements, comments and quotes on Tanning/Stainining developers; See Haist's Tanning Developer Section which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.
    Tom Hoskinson
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  5. #75

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    Quote Originally Posted by Tom Hoskinson View Post
    Jed, this is what the 1957 English edition of Han's Windisch's book says: "Owing to the small amount of sodium sulfite used, the developer has a tanning effect, producing negatives of a brownish color."

    It appears that this English translation from the German Edition was approved by Windisch.

    In any case, IF the "brownish color" Windisch describes was caused by re-deposited silver (as is the case with Kodak's Microdol-X Developer), it should be removable by bleaching (with a ferricyanide bleach).

    When I bleach a film developed in Han's Windisch's catechol developer, a tanned, stained, brown image REMAINS - QED

    Regarding page references for Grant Haist's statements, comments and quotes on Tanning/Stainining developers; See Haist's Tanning Developer Section which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.

    Tom, thank you for this information on the english edition of the book of Hans Windisch. It is not an accurate translation; because Windisch is not talking on a brown negative, but a brown image. And he is not referring to something like stain.
    According to your bleaching experiment the brown color is the result of a stain. Then I would conclude it might be a very fine stain. In the past it was thought that the brown color was the result the fine deposition of the silver, as is the idea about the warm color of prints. However, we cannot reject the idea of a very fine stain, considering what has been done in color photography.
    May be, there are two origins of the warm color. I would suggest, you inspect your bleached negatives with a microscope and describe your observation. And we have to be sure, the bleaching was 100 % perfect.

    With respect to the book of Haist: I can only find stuff on tanning, but nothing on staining. I can agree with the stuff on tanning. But the subject now is staining.

    Jed

  6. #76
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    The only experimental evidence missing from Tom Hoskinson's statement is what remains of the warm toned image from Microdl-X development after bleaching. Your comment should have been based on a simple test, not on conjecture that perhaps the warm part of the image will remain after bleaching.

    Any scientific background should include lessons in and practice of the scientific method. It is a proven fact that any system of axioms at least as rich as arithmetic is either incomplete or inconsistent or both. We cannot prove a theory. Our best bet is to try our best to disprove it. Instaed of searching for experimental proof that a theory is true, we must search for experimental evidence that for at least one case it is not true. Every case where the theory is applicable broadens the range of practical use of the theory. In other words, the scientist attacks his own theories with a vengeance. Part of your attack on your own theory should have been to bleach a Microdol X image to see what actually remains.

    Can we say that a single-agent developer always minimizes or eliminates edge effects? I think not. Any experiment aimed at finding the controlling factors of edge effects must be a multivariate one with developer composition, concentration, agitation technique and other factors.

    Now, if your purpose is only to correlate microscopic evidence of edge effect with subjective evaluation, be careful what you ask the subjective evaluators to do.
    Gadget Gainer

  7. #77

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    Quote Originally Posted by Jed Freudenthal View Post
    With respect to the book of Haist: I can only find stuff on tanning, but nothing on staining. I can agree with the stuff on tanning. But the subject now is staining.

    Jed
    Jed, emulsion gelatin tanning and staining are closely related topics. Your response tells me that you did not read all of Haist's Tanning Developer Section, which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.

    In particular, please read page 516 on the degree of gelatin tanning formation, which states in part:

    "...The departure from a constant relationship of relief and silver is probably attributable to side reactions such as stain formation in which the oxidation products are not wholly utilized in combining with gelatin."

    "Stain image formation is distinct from the formation of a tanned relief image. Stain results from two or more developer molecules reacting together in an oxidizing medium to yield a colored, insoluble product that is retained, imagewise in the gelatin. Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers, by combining with the oxidation products, but gelatin tanning is inhibited. Gelatin tanning occurs when the oxidized developer molecule reacts with a gelatin molecule in an oxidizing medium..."
    Tom Hoskinson
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  8. #78

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    Quote Originally Posted by Tom Hoskinson View Post
    Jed, emulsion gelatin tanning and staining are closely related topics. Your response tells me that you did not read all of Haist's Tanning Developer Section, which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.

    In particular, please read page 516 on the degree of gelatin tanning formation, which states in part:

    "...The departure from a constant relationship of relief and silver is probably attributable to side reactions such as stain formation in which the oxidation products are not wholly utilized in combining with gelatin."

    "Stain image formation is distinct from the formation of a tanned relief image. Stain results from two or more developer molecules reacting together in an oxidizing medium to yield a colored, insoluble product that is retained, imagewise in the gelatin. Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers, by combining with the oxidation products, but gelatin tanning is inhibited. Gelatin tanning occurs when the oxidized developer molecule reacts with a gelatin molecule in an oxidizing medium..."

    Tom, You are quoting Haist p.516. He describes the formation of stain in this quotation. Then he says Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers. Now, I observe stain in the pyrogallol developer and 'no' stain in the catechol developer. Both have sulfite in them, like the Hans Windisch developer. I would say that Haist is supporting the observation, although not explicitly, like 'there is no stain in catechol developers with sulfite in them'. Unfortunately there is no reference to the statement.

    I think Haist is referring to developers with one developing agent, because he calls pyrogallol an exception. If there are more developing agents in a developer, there is a greater chance to have a stain. And, there are many formulas around with more than one developing agent. There one might expect stain more readily.

    Jed

  9. #79

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    Quote Originally Posted by Jed Freudenthal View Post
    Tom, You are quoting Haist p.516. He describes the formation of stain in this quotation. Then he says Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers. Now, I observe stain in the pyrogallol developer and 'no' stain in the catechol developer. Both have sulfite in them, like the Hans Windisch developer. I would say that Haist is supporting the observation, although not explicitly, like 'there is no stain in catechol developers with sulfite in them'. Unfortunately there is no reference to the statement.

    I think Haist is referring to developers with one developing agent, because he calls pyrogallol an exception. If there are more developing agents in a developer, there is a greater chance to have a stain. And, there are many formulas around with more than one developing agent. There one might expect stain more readily.

    Jed

    Jed,

    It is not correct that pyrocatechin developers with sulfite will not stain. They will stain if the amount of sulfite level is not too high. However, if the sulfite level reaches a certain point, there will be no stain at all. Also, having experimented with pyrocatechin developers for a very long time, which has involved evaluating stain density in a variety of ways, including bleaching, I know for certain that there is a color density that remains in the negative after bleaching. I am reasonably confident (about 99.9% sure) that this is stain density, not a color caused by the size of the grains. If the latter were true, bleaching would not reduce the density. Why not just do the test yourself instead of quoting more studies? If you measure the negative first in Green, Blue and UV light, then bleach the negative, then re-measure with the same light, you will have the answer.

    Also, with regard to your statement, "if there are more developing agents in a developer, there is a greater chance to have a stain," I belive that this is wrong. It may have applied to one specific test that that for some reason you picked up on, but it is wrong as a general statement. I have done numerous tests varying the amount of metol, p-aminophenol and phenidone in pyrocatechin developers (with no-sulfite, or very low sulfite), and in every experiment the intensity of the stain image is greatest when pyrocatechin is the sole developer, and decreases steadily as the amount of the other reducers is increased. From the results of these experiments I must coclude that the notion that more developing agent increase the chance of staining in low-sulfite pyrocatechin developers is just plain wrong as a general rule. In fact, my empirical data suggests that the very opposite is true, i.e. the addition of a secondary reducer **decreases** the intensity of the stain. But you don't have to take my word for this. Just do the tests yourself and see what happens. Start with a 100% pyrocatechin developer, develop a step wedge negative and measure the stain, bleach, and then re-measure the stain. Repeat the test with varying amounts of a secondary reducer, say phenidone, metol and p-aminophenol.


    Sandy King
    Last edited by sanking; 02-13-2007 at 11:34 AM. Click to view previous post history.

  10. #80

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    Quote Originally Posted by sanking View Post
    Jed,

    It is not correct that pyrocatechin developers with sulfite will not stain. They will stain if the amount of sulfite level is not too high. However, if the sulfite level reaches a certain point, there will be no stain at all. Also, having experimented with pyrocatechin developers for a very long time, which has involved evaluating stain density in a variety of ways, including bleaching, I know for certain that there is a color density that remains in the negative after bleaching. I am reasonably confident (about 99.9% sure) that this is stain density, not a color caused by the size of the grains. If the latter were true, bleaching would not reduce the density. Why not just do the test yourself instead of quoting more studies? If you measure the negative first in Green, Blue and UV light, then bleach the negative, then re-measure with the same light, you will have the answer.

    Also, with regard to your statement, "if there are more developing agents in a developer, there is a greater chance to have a stain," I belive that this is wrong. It may have applied to one specific test that that for some reason you picked up on, but it is wrong as a general statement. I have done numerous tests varying the amount of metol, p-aminophenol and phenidone in pyrocatechin developers (with no-sulfite, or very low sulfite), and in every experiment the intensity of the stain image is greatest when pyrocatechin is the sole developer, and decreases steadily as the amount of the other reducers is increased. From the results of these experiments I must coclude that the notion that more developing agent increase the chance of staining in low-sulfite pyrocatechin developers is just plain wrong in my cases. In fact, my empirical data suggests that the very opposite is true, i.e. the addition of a secondary reducer **decreases** the intensity of the stain. But you don't have to take my word for this. Just do the tests yourself and see what happens. Start with a 100% pyrocatechin developer, develop a step wedge negative and measure the stain, bleach, and then re-measure the stain. Repeat the test with varying amounts of a secondary reducer, say phenidone, metol and p-aminophenol.


    Sandy King
    Excellent response, Sandy!

    Jed, please read Sandy's response carefully. I strongly recommend that you perform the testing Sandy describes in his last paragraph.
    Tom Hoskinson
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