> The M 1.7 is a bit sharper in the corners than the m 2.0 and is > the recommended lens, due to superior flatness of field, over the > 50 f 1.4's when using a bellows. I got rid of the only SMCP M 50 > 2.0 I ever owned after comparing the results to the SMCP-M. 50 > 1.7.
Yes, I don't think even Pentax recommends the 50/1.4 for flat-field work. You mention the M 50/2. I wonder how an A 50/2 work work. It is my opinion that the lens design that was changed the most from M to A models was the 50/2. The A 50/2 is quite a "best buy" for "almost generic" (<g>) 50's... Fred