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Thread: Over-coverage?

  1. #1

    Join Date
    May 2010
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    67

    Over-coverage?

    Can a lens with significant excess coverage degrade image quality through internal reflections? Obviously, the particular camera's internal construction will play a part for better or worse, but is this something to be concerned about?

    Would like to use a 10" Commercial Ektar on 4x5, possibly on a brand-new camera.

    Thanks,

    Mike

  2. #2

    Join Date
    Feb 2005
    Posts
    2,952

    Re: Over-coverage?

    Excess light can be controlled by using a compendium lens shade.

    Your 10" will work fine.

  3. #3

    Join Date
    May 2010
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    67

    Re: Over-coverage?

    cool...thanks!

  4. #4

    Join Date
    Nov 2006
    Location
    CA Central Coast
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    Re: Over-coverage?

    One can't be too rich, too thin, or have too much coverage

  5. #5

    Join Date
    Jan 2007
    Location
    Minneapolis, MN
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    1,255

    Re: Over-coverage?

    Quote Originally Posted by EdWorkman View Post
    One can't be too rich, too thin, or have too much coverage
    ... unless you're at the beach. Then the less coverage, the better... if you're rich and thin enough.

  6. #6

    Join Date
    Feb 2006
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    3,114

    Re: Over-coverage?

    St. Ansel covered this in "The Camera".
    One man's Mede is another man's Persian.

  7. #7
    Drew Wiley
    Join Date
    Sep 2008
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    SF Bay area, CA
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    14,577

    Re: Over-coverage?

    The answer is unequivocally YES, unless you deliberately want flare. That's why a lens
    shade, preferably bellows-style, is so important. But this is also a function of lens
    design, coatings, etc.

  8. #8

    Join Date
    May 2010
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    67

    Re: Over-coverage?

    Quote Originally Posted by E. von Hoegh View Post
    St. Ansel covered this in "The Camera".
    Which I can't say any of the local bookstores here in Bujumbura are likely to be carrying at the moment...and going out at night this week is a bit dicey with all the grenade attacks.

    So I guess I'll ask on the forum as I sit here on my couch.

  9. #9

    Join Date
    Feb 2006
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    3,114

    Re: Over-coverage?

    Quote Originally Posted by AgentX View Post
    Which I can't say any of the local bookstores here in Bujumbura are likely to be carrying at the moment...and going out at night this week is a bit dicey with all the grenade attacks.

    So I guess I'll ask on the forum as I sit here on my couch.


    Sorry - I forget that we're not all in a position to read whatever we like whenever we like.
    Say you are using a 300mm lens, with a 500mm image circle, on 4x5. You only need around a 160 mm image circle for the 4x5, so all this excess illumination will fall on areas other than the film causing loss of contrast, etc. It's known as "bellows flare" and can often be seen as an increase in density along the edges of the negative.
    The cure is a properly adjusted compendium shade, excluding all light except that coming from the scene you wish to record.
    One man's Mede is another man's Persian.

  10. #10

    Join Date
    May 2010
    Posts
    67

    Re: Over-coverage?

    That's exactly what seemed logical to me...looks like there might be a compendium hood in the classifieds I could use. Thanks for clarifying.

    Or I could just get a cheap 203 7.7 Ektar to use with the 4x5 instead of my big one.

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