So, mtf charts show a set of curves at f/8 and they are usually quite high up on the chart. Can we assume f/8 is the optimal aperture value for most lenses, in terms of contrast and resolution? I would guess that depends on the lens... But then, why f/8? And where would i find the "best" f/# values for each lens in terms of resolution and contrast?
The general rule is that a lens is sharpest two stops from it's maximum. So a faster lens can have it's optimal aperture at more like f/5.6 than f/8.Some lenses actually are sharpest at maximum aperture though- the 203mm f/7.7 Kodak Ektar large format lens being the only example I can think of. The best way to find out what the optimal aperture for your lens is just testing it on a tripod- take a bunch of shots at different apertures and compare. Empirical results are always better than MTF charts.
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