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  1. #81
    Photo Engineer's Avatar
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    Tom;

    That is what the data seems to show. The film has a certain characteristic and the data get that value in all developers within a small margin for error and some difference in developer. Of course, only 2 films were tested. We need data on more films to be certain.

    PE

  2. #82

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    That is the problem using data from the "old theory" method used by Altman-Henn and by Henry, by its very nature it leaves out adjacency effects and is biased in favour of solvent developers.
    Henry himself recognised this so here are a couple of quotes from his book:
    p214:"Since it is admitted that the sense of sharpness depends not only on acutance but also on adjacency effects, either the formula for acutance should be changed somehow or other to include edge effects, or a new term should be introduced to include both"
    This was never done so the old data remains misleading.
    p228:..X " states that an "acutance developer" cannot contain much sodium sulfite or other silver solvent. This is not true if we use acutance measurements as defined today (1986) as the criterion but may well be true if, as we said before,the adjacency effects are somehow included in the objective measurements of acutance"
    Using the 1986 conclusions is misleading.

  3. #83

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    This is why we've beein discussing Kriss and references to a way of incorporating edge effects in a more unified model of image definition. It is in both the definitions document and the summary of Henry's measurements I posted. I've repeated this a number of times.

    What you are referring to as the "old theory" is edge sharpness - ie the average gradient across the transition. Edge effects are something else - "microcontrast" effects that can, under some conditions, enhance the subjective impression of sharpness.

    What I'm proposing is that based on both experimental results and theory, the traditional concept of solvent "etching" reducing edge sharpness is at best a misrepresentation of the difference between solvent and non-solvent developers. Further, we cannot easily generalize because different films react in different ways.

    It would appear traditional acutance is primarily driven by exposure and film characteristics. The primary effects of developer choice are on graininess and in some cases, edge effects. I high pH, low sulfite developer such as Rodinal or Beutler tends to increase graininess significantly, and may give stronger edge effects than a mildly diluted solvent developer. So I would say the subjective characterization of these developers as sharp has much more to do with pronounced grain and edge effects than anything else, even if resolution declines. That seems to be what everything shows.

  4. #84
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    I once worked with a guy at EK who was working on high iodide emulsions for C41. He was also working on high solvent developers. By using both, he got extreme edge effects at high iodide. I have forgotten his work, but I remember that the edges were excessive. So, solvent + iodide can give edges.

    As for Kriss, our work at EK was directed toward including edge effects. I posted here two of Kriss' graphs showing edge effects and then plots of micro and macro contrast.

    These combinations mean that 35mm scale result often are no match for 4x5 results as the scales differ. A 45x contact printed can only be compared to a 35mm enlarged to that size. So there we have the problem of comparing macro vs micro edge effects and contrasts.

    PE

  5. #85

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    Some idea of the difficulty in trying to nail down adjacency effects is illustrated by Crane:

    http://proceedings.spiedigitallibrar...icleid=1232252

  6. #86
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    My question is... (if the differences are as subtle as both I believe them to be and this data seems to indicate that they are...)

    Might not tonal control of your negative, such that you are printing at a high contrast grade of paper (which increases mid-tone and micro contrast) actually deliver a higher perceived increase in sharpness than a change in negative developer?

    ~Forgive me if this should be a new thread but I don't feel comfortable starting it as I just do not have the technical knowledge to follow through with it properly.~

  7. #87
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    Shawn;

    You are correct. Higher contrast improves perceived sharpness. In fact, we used to go up about 1 grade in paper for each degree of magnification. So, contact grade printing = 2, 8x10 = 3, 16x20 = 4 and etc. This is an old trick which fits with your argument and that of others here, and no, this topic has not arisen.

    PE

  8. #88

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    Shawn, contrast is always related to sharpness, and ultimately we are concerned with how the print looks. So you are correct. Actually what you're suggesting is in line with what Crawley recommended for small format negatives - ie develop them to lower than normal contrast (and give the least amount of exposure required to secure adequate shadow detail under these development conditions) and print on a higher grade of paper.

    Of course we have to make sure we still get a negative that contains all the information we need to make a print with the desired tonal qualities, not just sharpness. But this goes without saying.
    Last edited by Michael R 1974; 07-05-2013 at 05:16 PM. Click to view previous post history.

  9. #89

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    Quote Originally Posted by Photo Engineer View Post
    Shawn;

    You are correct. Higher contrast improves perceived sharpness. In fact, we used to go up about 1 grade in paper for each degree of magnification. So, contact grade printing = 2, 8x10 = 3, 16x20 = 4 and etc. This is an old trick which fits with your argument and that of others here, and no, this topic has not arisen.

    PE
    PE,

    A slight caution here though in that I've found tonality and image quality can break down if a high grade of paper is needed for printing a negative even at limited magnifications. When using roll film I tend to expose at box speed (TMY-2) and process to not give overly bright highlights.

    Tom

  10. #90
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    Tome, you are entirely correct. I was assuming one negative at 3 sizes as a very very rough example.

    PE

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