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  1. #41
    RalphLambrecht's Avatar
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    Quote Originally Posted by wogster View Post
    I don't know if it's so much sharpness, as perceived sharpness, if you look at two images, the one that is measurably sharper may not actually look sharper. A brighter and higher contrast image can look sharper then an image that is darker and lower contrast, even though the second image may in fact be measurably sharper.
    Exactly!
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    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  2. #42

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    Quote Originally Posted by RalphLambrecht View Post
    Thanks for the details of your test. I wonder if you get into the wavelength of test light making a difference with these high resolutions.

    In any case, in my tests, I try to take some of the subjectivity out by taking a digital photograph through the microscope and then normalize the exposure in Photoshop. Then, I take the eye-dropper tool to find the line pair with a 10% difference in 'density' between a black and white bar, and use that for the resolution calculations.

    I also think that PE is correct in saying that all test taken with the same lens eliminate the effect of optics and are valid. The benefit of that approach is also that it makes the test and the results more realistic. Who cares about a 200 lp/mm performance if you can only get it from contact printing a $500 resolution target? OK to compare emulsions or developer effects, but how much is left of the material difference after a camera lens took care of it?
    The only step I took with regard to the wavelength was to balance the exposing light to daylight.

    I agree that practical tests for resolution made in the camera give a more realistic indicator of the capability of the film/camera/lens system. However, if the weak link in the chain is a lens that can not resolve more than 100 lpm a test for resolution with developers will not reveal any useful information about resolution if all of the film/developer combinations tested are capable of more than 150 lpm, which was the case in my testing.

    Ultimately perceived sharpness is more important than any other single factor, as has been pointed out. I have made prints 12X18" in size from a Canon G9 (7mm wide sensor) that look sharper, at viewing distance of 10-12", than some prints I have made from 5X7 negatives that have a huge amount of detail.

    BTW, I print with a hybrid process. Either film or digital capture, mostly the former, correction in Photoshop, printing a digital negative, and finally a carbon transfer print. The file is adjusted with a curve to give a digital negative with a totally linear output so that what I see on screen is pretty much what I get in the final print, regardless of whether the original capture is film or digital.


    Sandy King
    Last edited by sanking; 06-15-2009 at 07:40 PM. Click to view previous post history.

  3. #43

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    Quote Originally Posted by voceumana View Post
    Aldevo,

    I think you have it exactly right, except that D-76 is considered a moderately fine grain developer rather than an accutance developer. For the best resolution, you probably don't want the highest accutance developer. Best resolution is usually acheived with a lower contrast light-to-dark transition, whereas highest accutance is acheived with a higher contrast light-to-dark transition.

    Charlie Strack
    Understood. It's my understanding that D-76 is not heavily-reliant on the so-called solvent effect to achieve fine grain. Earlier fine grain developers, such as those using PPD, were heavily reliant on the solvent effect.

    Your explanation of resolution vs contrast is exactly what I would expect. Unsharp masking in Photoshop is probably nothing more than accentuating local contrast gradients around areas that meet some candidate contrast threshold.
    Digital Photography is just "why-tech" not "high tech"..

  4. #44

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    Quote Originally Posted by Thomas Bertilsson View Post
    I agree with Ron. These results are technical and can usually be measured. Unless it's measured it's subjective and fairly useless for anybody else.
    I do feel that people put too much energy and thought into film developers. Pick one and work with it. By varying your technique, evaluating your results, and above all - printing your negatives often, you learn a lot.
    The other week I shot two rolls of Kodak TMY (the old kind) using a 35mm camera. I processed one roll in Rodinal and the other in Xtol. According to what everybody claims they observe with these two developers, the difference in grain should be huge. In reality, in the resulting 11x14 prints, the difference (to my eyes) is really negligible. Sharpness was very similar too. I used a Rodenstock Rodagon enlarging lens, which is an OK lens, so no sub-par equipment either.

    What I'm getting at is that if you're truly interested in resolution, sharpness, grain, acutance and all that, at least make an evaluation based on how it makes a difference for you in practical terms before you take it too far. I found, by comparing prints of the normal size I make them, that I don't really care whether I get the look of the Rodinal or the look of Xtol. As an artist the difference between them is not even close to feeling important, that's how subtle the difference is. It may be different for you, but it's worthwhile comparing prints before you get overly concerned with which film developer you use.

    - Thomas
    Great points, all.

    I've finally learned not to obsess about such things because I never enlarge my negs beyond about 9x and, most frequently, never beyond 8x. The differences in sharpness & grain between developers at relatively modest enlargements will not be significant.

    Shifting gears a bit it certainly appears that the limits of resolution are only attainable under highly-optimized conditions that can only be realized in a heavily-controlled environment. We never realize such conditions in the field.
    Digital Photography is just "why-tech" not "high tech"..

  5. #45
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    Quote Originally Posted by aldevo View Post
    Your explanation of resolution vs contrast is exactly what I would expect. Unsharp masking in Photoshop is probably nothing more than accentuating local contrast gradients around areas that meet some candidate contrast threshold.
    That's exactly how it works, it's tough to get it right though, there are lots of digital images that have been over sharpened.
    Paul Schmidt
    See my Blog at http://clickandspin.blogspot.com

    The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....

  6. #46
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    Quote Originally Posted by sanking View Post
    The only step I took with regard to the wavelength was to balance the exposing light to daylight.

    I agree that practical tests for resolution made in the camera give a more realistic indicator of the capability of the film/camera/lens system. However, if the weak link in the chain is a lens that can not resolve more than 100 lpm a test for resolution with developers will not reveal any useful information about resolution if all of the film/developer combinations tested are capable of more than 150 lpm, which was the case in my testing.

    Ultimately perceived sharpness is more important than any other single factor, as has been pointed out. I have made prints 12X18" in size from a Canon G9 (7mm wide sensor) that look sharper, at viewing distance of 10-12", than some prints I have made from 5X7 negatives that have a huge amount of detail.

    BTW, I print with a hybrid process. Either film or digital capture, mostly the former, correction in Photoshop, printing a digital negative, and finally a carbon transfer print. The file is adjusted with a curve to give a digital negative with a totally linear output so that what I see on screen is pretty much what I get in the final print, regardless of whether the original capture is film or digital.


    Sandy King
    That makes sense to me because it reflects my experience as well.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

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