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  1. #1
    Mustafa Umut Sarac's Avatar
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    Leitz minus aberration meaning

    I found that leitz summitar have negative spherical and coma aberration . Is negative aberration good thing or bad thing and if it is a good thing , how it comes at a picture ?

    Umut

  2. #2
    David Lyga's Avatar
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    Mustafa, the only thing I can say regarding this 'negative' formulaic determination is that it just might balance out the other elements. So many elements are used to counter the bad effects of the others. That is why (especially) wide angles have so many surfaces: wides are the most difficult to correct. Read this:

    http://www.lensrentals.com/blog/2010...ly-aberrations

    - David Lyga

  3. #3
    Mustafa Umut Sarac's Avatar
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    David, yes, negative, positive aberrations are used for balance each other. But it opens a new questions , is it explains everything. I have a Ektar ,my mother and I agree , when you look from the back of the lens , skin details, shadows, lines, 3d curves are faraway being increased and visible. Faraway, different than the eye sees. Why ? Are these high aberrations and compensartions used for something also ?

    Umut

  4. #4
    ic-racer's Avatar
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    Nomenclature for negative and positive coma and spherical aberration.
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    Is negative aberration good thing or bad thing
    Personally I prefer positive coma, where it seems to point into the picture frame, rather than pointing outward.
    Last edited by ic-racer; 09-04-2013 at 06:31 PM. Click to view previous post history.

  5. #5
    Mustafa Umut Sarac's Avatar
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    ic-racer,

    Thank you very much, first time I have ever saw such graphs. Can you explain first graph and your preferenment ?

    Umut

  6. #6
    Mustafa Umut Sarac's Avatar
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    That is interesting about sph. aberration.

    Since the effective focal point determines the position of the image for any object, the fact there are several different focal points for the different kinds of rays means that there are several “ghost” images formed by the lens – the “real” one determined by the location of the paraxial-ray focal point, and a number of other images that are formed at different distances depending on where the rays that form them struck the lens.

  7. #7
    Mustafa Umut Sarac's Avatar
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    negative coma

    when coma is negative, the image produced by the off-axis rays is slightly smaller.

  8. #8
    ic-racer's Avatar
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    Quote Originally Posted by Mustafa Umut Sarac View Post
    ic-racer,

    Thank you very much, first time I have ever saw such graphs. Can you explain first graph and your preferenment ?

    Umut
    Positive coma. They point inward toward the center.
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  9. #9
    IloveTLRs's Avatar
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    Quote Originally Posted by ic-racer View Post
    Positive coma. They point inward toward the center.
    Click image for larger version. 

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    So that's what that is called. My Summitar has displayed this effect, shot at f2 at infinity. I can't say I like the effect at all.
    Those who know, shoot film

  10. #10
    Mustafa Umut Sarac's Avatar
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    How do you analysis below charts of Leitz Wetzlar Summitar Design Analysis ?

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