09-07-2011, 11:24 AM
[quote name='PuxaVida' timestamp='1315392517' post='11380']
This lens resolves ~500lp/mm for the 12mm part of the image circle. Did you find it remarkably worse on the edges, or is it still stellar (on APS-C)?... I mean concerning the other images you've taken....
[/quote]
The 500lp/mm only is valid for monochromatic light (e-line), but still out-resolves DSLR lenses. This lens is diffraction limited, basically. Theoretical max. resolution for f2 for e-line monochromatic light is 750 lp/mm, for f2.8 536 lp/mm down to f8 (smallest aperture this lens has) of 188 lp/mm. The lens then can resolve more at 2f and f2.8 than it can at f4, f5.6 or f8.
Those figures for the center 12mm at 1:4 are of course stellar, but that does not mean that they nosedive for the rest of the frame.. still sharp towards the edges.
I do notice a slight amount of coma or astigmatism on the edges at times, which i will have to look into deeper... but nothing to get worried about. Note that I use the lens at about 1:2 instead of its designed 1:4. When I find a thin M39 to EF mount adapter I will be able to get closer to its 1:4 purpose to really see what it can do.
This lens resolves ~500lp/mm for the 12mm part of the image circle. Did you find it remarkably worse on the edges, or is it still stellar (on APS-C)?... I mean concerning the other images you've taken....
[/quote]
The 500lp/mm only is valid for monochromatic light (e-line), but still out-resolves DSLR lenses. This lens is diffraction limited, basically. Theoretical max. resolution for f2 for e-line monochromatic light is 750 lp/mm, for f2.8 536 lp/mm down to f8 (smallest aperture this lens has) of 188 lp/mm. The lens then can resolve more at 2f and f2.8 than it can at f4, f5.6 or f8.
Those figures for the center 12mm at 1:4 are of course stellar, but that does not mean that they nosedive for the rest of the frame.. still sharp towards the edges.
I do notice a slight amount of coma or astigmatism on the edges at times, which i will have to look into deeper... but nothing to get worried about. Note that I use the lens at about 1:2 instead of its designed 1:4. When I find a thin M39 to EF mount adapter I will be able to get closer to its 1:4 purpose to really see what it can do.