Members might have seen that the 40mm f/2 Nikkor has captured my attention of late, and then for IR which it does in an excellent manner. However, what about general performance for ordinary photography? Nikon does not specfify the lens as top-of-the-line 'S', and the MTF curve bears this out. However we tend to take few photos by an MTF curve alone, so more practical avenues have to be pursued.
I usually start by checking performance up close, since I frequently shoot suchlike scenes. Thre 40mm has a maximum reproduction ratio of 0.17 or 1:5.9X. Thus close but no cigar, to follow that metaphor. It is obviously not a flat field design, as might be predicted form its design, and there is some mild astigmatism to the outer part of the frame as well for close-ups. However, colour aberrations are pretty well kept under control, so in a pinch, one can get a decent close-up with the 40mm.
(I now realise this image also is an RGB example
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