# Leitz minus aberration meaning

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• 09-04-2013, 05:18 PM
Mustafa Umut Sarac
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
• 09-04-2013, 05:42 PM
David Lyga
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
• 09-04-2013, 06:05 PM
Mustafa Umut Sarac
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
• 09-04-2013, 06:17 PM
ic-racer
Nomenclature for negative and positive coma and spherical aberration.
Attachment 74017
Attachment 74018

Quote:

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.
• 09-04-2013, 06:38 PM
Mustafa Umut Sarac
ic-racer,

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

Umut
• 09-04-2013, 06:47 PM
Mustafa Umut Sarac
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.
• 09-04-2013, 06:49 PM
Mustafa Umut Sarac
negative coma

when coma is negative, the image produced by the off-axis rays is slightly smaller.
• 09-04-2013, 07:53 PM
ic-racer
Quote:

Originally Posted by Mustafa Umut Sarac
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.
Attachment 74023
• 09-05-2013, 01:23 AM
IloveTLRs
Quote:

Originally Posted by ic-racer
Positive coma. They point inward toward the center.
Attachment 74023

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.
• 09-05-2013, 10:09 AM
Mustafa Umut Sarac
How do you analysis below charts of Leitz Wetzlar Summitar Design Analysis ?

Attachment 74032

Attachment 74033

Attachment 74034

Attachment 74035
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