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  1. #31

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    Quote Originally Posted by gainer
    ...we should consider other approaches. One is to print the negative of the step wedge on the printing material in question and note the number of steps between black and white.
    Patrick, it all really comes down to what kind of precision, accuracy, and predictability we want. Sure, using paper works. Afterall, we are trying to make prints. And it would be foolish not to verify that measurements made with a densitometer did not behave as expected on the printing paper.

  2. #32
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    Quote Originally Posted by Kirk Keyes
    Patrick, it all really comes down to what kind of precision, accuracy, and predictability we want. Sure, using paper works. Afterall, we are trying to make prints. And it would be foolish not to verify that measurements made with a densitometer did not behave as expected on the printing paper.
    Of course. But if you use a 30 step 0.1 wedge, you get within + or - 0.1 in estimating the SBR that your developing procedure and film could put on your chosen paper. It's not likely that two people will agree with each other that closely on measured SBR at the original scene.

    If you are trying to define very small differences between films or processes for scientific purposes, then it is necessary to be very specific about the experimental conditions, including the specs of all measuring instruments. I could preach about this aspect of experimentation from my experience at writing and editing NACA and NASA research papers, but I won't because I'm sure it would be like preaching to the choir.

    When I have an idea for some test that I think should be done, I may do a quick and dirty trial to see if it's worth pursuing. In a group like this, I might publish that Q&D work as such because the more people you can get to try something, the more likely the final result is to be valuable for either accepting the premise or rejecting it.

    So I wound up preaching anyway. Oh well, I guess I have achieved what I never thought would happen. I'm old.
    Gadget Gainer

  3. #33

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    Patrick, I'm in that choir!

    And Quick & Dirty testing does have a place. Even using a step wedge is more testing than probably 99+% of photographers will do.

    But as I said, it's all a matter of what kind of precision, accuracy, and predictability someone wants.

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