Apertures for Len Stacking?

Discussion in 'Digital SLR' started by Wilba, May 16, 2010.

  1. Wilba

    Wilba Guest

    I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7 reverse
    mounted on a Canon EF-S 55-250mm at 250. I'm going to do some testing to
    find the best combinations of apertures for maximum DOF and IQ without
    obvious diffraction. Where would you start with the apertures? I want to
    hear something like, use the same aperture on both lenses, tight on the
    primary and wide on the reversed, the other way around... what has worked
    for you with that kind of setup?

    I don't have a problem with stopping down the reversed lens - I have enough
    light on the subject.
     
    Wilba, May 16, 2010
    #1
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  2. Wilba

    Paul Furman Guest

    Stop down the front 50mm lens. Here's a discussion of almost the same
    setup you describe:
    http://www.photomacrography.net/forum/viewtopic.php?t=8336
    Figure out the best aperture by testing.

    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
     
    Paul Furman, May 16, 2010
    #2
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  3. Wilba

    Wilba Guest

    Thanks a bunch, just what I was looking for.
    Now I have a strategy for a test - set the primary aperture to its widest
    and find the optimal aperture on the reversed lens. Then I'll see if
    stopping down the primary aperture makes a difference for that reversed
    aperture.
     
    Wilba, May 16, 2010
    #3
  4. Wilba

    Paul Furman Guest

    As a starting point, effective aperture at about 4x like that will be...
    (assuming the zoom is f/5.6 on the long end) ...

    f-number (magnification +1)
    5.6 (4+1) = f/28

    But there's plenty of variables & things to mess up that math.

    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
     
    Paul Furman, May 16, 2010
    #4
  5. Wilba

    Wilba Guest

    I'm doing this to do photos, not maths. :-D

    F/8 on the 250 and f/9.5 on the 50 gave the best results today.
     
    Wilba, May 16, 2010
    #5
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