Roger Cicala looks at lens, camera and autofocus variation
Roger Cicala of LensRentals has written an article about lens and camera sample variation. The latest article builds on the several excellent pieces he's already written by subjecting a series of lenses to studio testing. As one of the few independent people in a position to test and assess sample variation with a reasonable sample size, it's well worth a read. As with all his posts, it does a good job of explaining and demonstrating the inherent variability and inconsistencies in lens behavior. It also addresses the reasonable desire (and sometimes unreasonable behavior) of photographers to get a 'good copy' of a lens.
And, for a little more background, we'd also recommend the articles that led up to this latest one:
'"This lens is soft" and other myths' - which looks at reasons why users may conclude their lens is faulty, even though it isn't.
'"This lens is soft" and other facts' - which looks at some of the reasons behind poor lens/camera results.