Talk:Anastigmat
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Most modern lenses are close to being anastigmatic by old standards. Still the sagittal and meridional focusing "planes" (they tend to be complex curves aproximating a plane) are distinct, and that shows in the MTF charts. Some lenses suffer more from this aberration than others. For example, from my personal experience the 18-50 f/2.8 EX from Sigma is a lens that must be focused between those planes or otherwise will produce very sharp images in the center but not at all in the edges. If properly focused it is very sharp all over, since astigmatism gets masked. I've also found many reports complaining about "back focusing" and "front focusing" are really astigmatism. That's why I corrected the article. Rnbc (talk) 19:17, 5 February 2008 (UTC)
Design - questionable statement
[edit]The statement
[...A]spheric surfaces are more costly to manufacture than spherical and other conic section (hyperbolic, parabolic) ones.
implies that aspheric surfaces are not conic sections (in cross section). In fact they can be either conic or not. A conic section does not by itself imply ease of manufacture. The only surfaces I know of that can be generated easily by basic grinding methods are flats and spheres.
I would simplify this statement to:
[...A]spheric surfaces are more costly to manufacture than spherical ones. Morycm (talk) 01:06, 29 May 2026 (UTC)