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  1. #21
    nick mulder's Avatar
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    Quote Originally Posted by steven_e007 View Post
    I have a horrible feeling to be sure would involve... calculus . Let's not go there!.
    No please, lets !

    Perhaps just work with a couple of triangles and a rectangle for focal plane ?

    But the integrals involved with leaf shutters ? hmmm
    Cleared the bowel problem, working on the consonants...

  2. #22

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    Quote Originally Posted by nick mulder View Post
    No please, lets !

    Perhaps just work with a couple of triangles and a rectangle for focal plane ?

    But the integrals involved with leaf shutters ? hmmm
    Be my guest... as long as I don't have to work it out myself!!!

    The overall point of all this, I think, is that you can't just measure shutter speed with a tester like you measure temperature. Really, you need to test for the effect you want photographically. I've seen many people complain that compur style fast shutters only achieve 1/350sec when set to 1/500 - as if that is a huge error. In reality you should do a reciprocity test, on film, against 1/250 and 1/125 (stopping the lens down each time). Quite probably the slow speed compensates for the low efficiency. As long as the 1/500s setting gives us about have the exposure of 1/250 - then as photographers we should be happy?
    Steve

  3. #23
    RalphLambrecht's Avatar
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    I don't know, but I don't like the idea of relying on two wrongs making a right.
    Regards

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

  4. #24

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    Quote Originally Posted by RalphLambrecht View Post
    I don't know, but I don't like the idea of relying on two wrongs making a right.
    But I think with the inherent shortcomings in certain shutter designs, there necessarily has to be a few wrongs, so maybe better to try to get them to cancel each other out?
    Steve

  5. #25
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    Quote Originally Posted by steven_e007 View Post
    But I think with the inherent shortcomings in certain shutter designs, there necessarily has to be a few wrongs, so maybe better to try to get them to cancel each other out?
    Try to cancel them out?

    What if they add up?
    Regards

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

  6. #26

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    Quote Originally Posted by RalphLambrecht View Post
    Try to cancel them out?

    What if they add up?
    Then you'd have to stamp a very different shutter speed on that setting for your shutter!

    When I tested a rebuilt 'front of lens' roller blind shutter (circa 1870ish or something) on the front of an old Sanderson, I was amazed that the shutter speeds seemed to be about right. Now I think about it I reckon the numbers stamped on the dial had little to do with the actual time the shutter opened for... but the resulting exposure was in the right ballpark, so I was happy
    Steve

  7. #27
    RalphLambrecht's Avatar
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    Quote Originally Posted by steven_e007 View Post
    Then you'd have to stamp a very different shutter speed on that setting for your shutter! ...
    That works for focal-plane shutters, but keep in mind the timing of a leaf shutter depends on the aperture setting. With leaf shutters, the effective exposure time at small apertures is longer than at large apertures.
    Regards

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

  8. #28

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    Quote Originally Posted by RalphLambrecht View Post
    That works for focal-plane shutters, but keep in mind the timing of a leaf shutter depends on the aperture setting. With leaf shutters, the effective exposure time at small apertures is longer than at large apertures.
    That of focal plane shutters too (though perhaps to a lesser degree).
    With larger apertures, the spread to the left and right of the slit aperture will be more than with smaller aperture, thus the exposures will be longer.

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