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  1. #11
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    Kodak gives MTF which has a direct correlation with sharpness or resolution.

    See here, Page 18: http://www.kodak.com/global/en/profe...4016/f4016.pdf

    and here: http://www.normankoren.com/Tutorials/MTF.html for some interesting information.

    PE

  2. #12
    AgX
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    Thanks, I know that Koren tutorial It is very informative, but I haven't looked at it for a while as I have to admit with a large pile of books and a the computer filled with files it is sometimes hard to decide where to look for something.

    However it does not give listing of colour paper resolutions as far as I remember.
    And that first link leads me to the T-max data-sheet.

  3. #13
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    All of Kodak data sheets for all film have MTF data. No data is reported nor has ever been for ANY paper AFAIK, as the reading of reflection MTF is very very difficult and fraught with possible error due to viewing angle and other factors including reflectance substrate (RC vs Baryta for example). It is also tied up with magnification of the image and viewing distance whereas film values are an absolute (relatively speaking ).

    PE

  4. #14

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    Thanks, it turns out that an MTF curve is available for Velvia 50 from Fuji's data sheet. The curve doesn't go above spatial frequencies of about 60 lpm (line pairs or cycles per mm). I used Koren's procedure of parametrizing the curve and duplicated the curve provided by Fuji with the frequency axis extended to 200 lpm.

    Converting from the USAF chart to an MTF is very risky, since the selection of the pattern which is considered barely resolvable is a very subjective matter and usually corresponds to an MTF (contrast) of from 2% to 5%. Taking 5%, the USAF chart-derived resolution of Velvia 50 is about 140 lpm. This is 4 times what I observed in my test.

    Warren N

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    Did you use a vacuum frame or pressure frame to hold the film against the chart?

    Was it the evaporated metal USAF chart?

    Those questions are also important in this evaluation. It is not clear how your test was actually performed.

    PE

  6. #16

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    My procedures were not very sophisticated. I used a cardboard chart which I purchased from Edmund Scientific and photographed it outside on our deck from a distance of about 10 feet. I have used the same technique on a number of occasions in the past to evaluate my lenses and obtained the expected resolutions of about 70 lpm. I should do it again with fresh film and using more careful procedures.

    Thanks for the suggestions.

    Warren N

  7. #17
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    Well, I can probably solve part of your problem then.

    The data reported by Kodak and Fuji are for the film, in vacuum contact with a metal deposited chart emulsion to metal. Your data includes the MTF of the lens since you used a camera. So, you need OTF (O = Optical) in the mix.

    PE

  8. #18

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    I believe that the resolutions add reciprocally (like resistors in parallel), so my observed resolution should be 1/(1/70+1/140)=47 lpm, not too far from what I observed. Thanks!

    (MTF vs frequency functions are multiplied, like any transfer function.)

    Warren N

  9. #19
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    Quote Originally Posted by warrennn View Post
    Thanks, I should make 11x11 prints to prevent the paper resolution from being the limiting step.

    Do you have any idea why an E6 transparency would have much lower than expected resolution?

    Warren N
    The low-contrast figures are the most useful resolution, in the case of Velvia which has the highest it is 80 lp/mm iirc, about the same as the 30D and 5D II are capable of at maximum given good lenses to put in perspective if that helps.

    High-contrast resolution is useful for some things, but you should base all yuor expectations on the low-contrast resolution, which is what you'll see across the texture of an object etc.

    In which case, C-41 is up there with E-6 in low-contrast resolution iirc from looking at the Fuji specs.

  10. #20

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    Quote Originally Posted by warrennn View Post
    Thanks, I should make 11x11 prints to prevent the paper resolution from being the limiting step.

    Do you have any idea why an E6 transparency would have much lower than expected resolution?

    Warren N
    Hi Warren,

    as I have explained in my first post, resolution of Velvia at medium contrast is a little bit lower compared to TMX.
    At low contrast of about one stop (1:2) Velvia 100 and Velvia 100F even have higher resolution than TMX. TMX is rather grainy compared to the extremely fine grained Velvia 100, Provia 100, E100G, Astia 100F and so on.
    At these low contrast values the resolution of TMX is limited by the much coarser grain, the ISO 100 slide films all give much better detail as TMX at this low contrast.

    So, there must be a test mistake in your set-up.

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