> Is it accurate to conclude that the slower the lens, the flatter > focusing field? The 50/4 is flatter than the 50/2 is flatter than > the 50/1.7, et cetera?
Well, I imagine that your generalization is probably true most of the time, within a group of otherwise similar lenses. I would suspect that, say, in the A 50's, the field of the f/2 might be slightly flatter than that of the f/1.7, which in turn is almost certainly flatter than that of the f/1.4, with the field of the f/1.2 very possibly showing the most curvature. (Just a hunch...) However, the M 50/4 Macro does not have a flatter field primarily because it is a slower lens (although that may be a contributing factor) - it has a flatter field because it was specifically designed as a ~macro~ lens (i.e., a lens which has to focus close, of course, but which also should be able to render a flat plane of focus properly. (Just another hunch...) However, I wouldn't be surprised if both the newer A 50/2.8 Macro and the even newer F/FA 50/2.8 Macro have an even flatter field, despite being faster than the f/4. (And still another hunch...) Fred - 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 .
