>But I do have a few questions about this stuff. Why should a lens perform
>worse from 5-10 ft as opposed to infinity? Isn't the focus just moving the
>elements back and forth? I know there must be some zooms/CRC designs where
>closer would be different, but this isn't most lenses. And since a lot of
>shots may be taken at a close distance, is this not then a fair test of
>lens performance? IE, if most lenses perform better at infinity than at
>25-50x, then don't all lenses have the same disadvanatge by being tested
>closer? Just wondering your thoughts?

Um, I have been (gently) hollering about this for some time: lenses do
NOT perform uniformly with distance, NOR do they vary in the same ways.
ALL lenses have an optimum design distance, and most perform differently
at the same distances away from it. IF it were possible to do a perfect
and repeatable chart test, it would STILL not represent the lens performance, unless it could be done at the optimum distance (could be infinity!), or a uniform set of distances, or a uniform proportionally varied set of distances related to lens angle-of-view, or some such.
(Symmetrical, simple lenses change the least with distance, odd-number
element lenses are very noticeably more sensitive, and zooms can be
extremely sensitive [note comments on some lenses in "SLE(MN)" related
to performance and distance].) I am amazed that distance-sensitivity is
not (apparently) considered in traditional lens testing, though the
effect is generally recognized (though not accomodated).