Archived posting to the Leica Users Group, 1998/06/06

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Subject: Re: [Leica] sharpness, was New 50 R Summilux
From: TEAShea@aol.com
Date: Sat, 6 Jun 1998 14:52:09 EDT

<< surely the influence of the lens design would play a much greater
 factor than the focal length ? (this talk of APO lenses for instance,
 if the lens is "non-APO" then there would be a color cast along the
 edge (thereby broadening it) ? and i don't see APO short-focal-length
 lenses, so is it axiomatic that short focal lengths don't require 
 color correction in the same way long-focal-length lenses require it ?) >>

You are correct.  Short telephoto lenses are the least difficult to design.
One does not need to be as concerned with the apochromatic design of lenses
shorter than about 80 mm in focal length.  While the laws of physics / optics
still apply to these lenses, the effect of chromatic aberrations are less easy
to detect.