I've order the Sigma 70-300 APO Macro. Lenses in this range are always weakest at the long end, and I want to shoot for maximum possible sharpness at 300 mm. Popular Photography reviewed the lens in the March 2000 issue. They say that at 300 mm. and closest macro distance (a bit less than 1 m.), the lens is sharpest at f5.6. According to the table showing SQF/MTF, though, the lens at 300 mm. is clearly sharpest at f16.
So, are the SQF/MTF tables done at some distance other than closest focus? Which distance? How do I calculate where, on the distance scale, the sharpest aperture changes from f5.6 to f16 at 300 mm? Thanks very much, Joe - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
