Gary,
What you said is true (with regards to 'knowing' the relative focus point due
to curvature of field). However, that wasn't really the direction of my
question. Testing is fundamentally flaw for numerous reasons mentioned however
it can present some relative information between lenses. Alas, in reality you
(well I) rarely photograph flat surfaces that occupy the full frame or things
at infinity. So - even 'real' tests of flat surfaces in the range of
1:8 to 1:20 are likely to be non-indicative of lens performance.... Though I
guess I have to admit that in many of my 3d pictures the center tends to be
closer and the edges further which enhances any lost of sharpness due
curvature. You'd (well I) would almost prefer the curvature of focus
to be inversed when it is desired to have sharpness from center to edge...
Alan
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