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  1. #51
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    Yes Bill, it can. I believe that there is another thread on this.

    However, the data then becomes a square wave instead of a sine wave of noise which represents the grain. IDK if that is what I really want. Kriss discusses this and I have to do more studying and bone up on my Calculus and DE.

    PE

  2. #52

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    PE, do the sharpness aspects of Kriss's image content model relate to MTF in any way?
    Last edited by Michael R 1974; 06-24-2013 at 03:40 PM. Click to view previous post history. Reason: Clarity

  3. #53

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    Quote Originally Posted by Alan Johnson View Post
    I did investigate the difference between 3-min agitation intervals and stand development:
    http://www.apug.org/forums/forum37/5...velopment.html
    Nowadays I use Don Cardwell's recommendation from his reply.
    Alan, for some reason I missed this earlier. Very interesting test. Just to clarify re Henry's tests, when there was pre-exposure he did find statistically significant fringe effects even with D-76. With no pre-exposure perhaps the problem is that he did not investigate longer agitation intervals than 1 minute, while your test started with 3 minute intervals. Or it may be he did not find any statistically significant edge effects. It also may be there is more density in the low density side of your negative than you thought. I think it makes some sense to expect a fringe effect of some kind even at base fog, but it would likely be very small so who knows.

    Henry used a variety of developers including Beutler and Rodinal and refers to these tests on p. 226. In fact his Rodinal tests were quite interesting. The developer produced more pronounced edge effects and higher granularity than D-76 1:1 with Pan-X and Tri-X, but not higher acutance.

  4. #54
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    Quote Originally Posted by Michael R 1974 View Post
    PE, do the sharpness aspects of Kriss's image content model relate to MTF in any way?
    Yes, his work does incorporate MTF.

    PE

  5. #55
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    Quote Originally Posted by Michael R 1974 View Post
    Henry used a variety of developers including Beutler and Rodinal and refers to these tests on p. 226. In fact his Rodinal tests were quite interesting. The developer produced more pronounced edge effects and higher granularity than D-76 1:1 with Pan-X and Tri-X, but not higher acutance.
    Thank you for pointing this out, Michael.

  6. #56

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    Before posting a summary of some of Henry's acutance and granularity data for discussion, I thought it might help to post some "primer" definitions for anyone not entirely familiar with the terminology. I tried to keep it simple but welcome any feedback - and corrections. I'm thinking a few diagrams might help. Perhaps if this is well received we can post it as an article. As a second step I'm working on a kind of "map" showing the various variables (film characteristics, developer characteristics etc.) and how they are interrelated.
    Attached Files

  7. #57
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    Michael:

    Thanks for this. I've only had time to read through it once, but it appears to be very useful.

    I certainly haven't seen any need for corrections, but I did smile when I noted that the list of "Definitions" starts out with a definition for "Definition".
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  8. #58
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    Is acutance is a measure for print or film only , or does it explain the lenses also. Is there a way to measure acutance of a lens , or film , paper or does it specific to the only single taken picture ?

  9. #59

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    Umut, acutance as I've described it is meant to be an objective measure of edge sharpness in a film or print emulsion. This is why the test on a film (for example) involves "direct" exposure without a camera lens. It is less straight forward with a print, but ultimately the guiding principle with image structure characteristics is to find measurements that correlate well with subjective impressions when viewing prints. Resolving power is complicated because in the end one is interested in the resolving power of the system. MTF is a more sophisticated measure of resolution incorporating contrast and is often used to evaluate optical systems/lenses.

    In the document I dealt with image definition as it pertains to films and processing. Optics are not really considered in that context as they are essentially assumed to be a non-limiting constant in tests. Obviously in actual photography optics are important.

    PE could comment further on the work of Kriss which seems to be a combination of the objective characteristics correlating with subjective impressions (resolving power/modulation transfer, acutance, edge effects, granularity) into an overall measurement of image quality called "image content". As noted in the document these characteristics can be interrelated, which is presumably why Kriss's model requires some fairly complex math.

  10. #60

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    Attached is a summary of some of Richard Henry's acutance and granularity tests. I've also re-attached the "definitions" as a PDF.

    I've included some of Henry's conclusions based on the data. I'm not saying I'm necessarily in agreement with him in all cases, and there are some questions I would have liked to ask him, issues to raise etc. One must keep the context of Henry's book in mind. He set out to prove or disprove technical assertions and claims made throughout the photographic literature since, as he correctly points out, for the most part we are asked to ignore research from companies like Kodak and instead rely on what people say even though they present no data, do not explain their tests, and often lack any scientific or even reasonable basis for their claims.

    In all honesty I think the first half of the book dealing with print controls is more complete and better presented. The second half of the book - from which the attached data comes - leaves me with many questions. Nevertheless it highlights some important issues, and should make us think a little more critically when people say things like "Rodinal is sharp", or "D-76 is mushy". Do people know what sharpness is? Are their perceptions even honest or are they coloured by what they've been told is true? Etc.

    Michael
    Attached Files



 

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