Fred wrote: > I'm not so sure about that. From my experience, generally only the > longer telephotos (300mm and longer, usually) focus past infinity to > allow for thermal changes. I believe that, for shorter lenses, the > effects of heating and cooling are so small, and the DOF ample > enough, that there is no need for focusing past infinity (and such a > provision seems to be lacking in such lenses).
Not really. I looked into this in order to get my Limited lenses (all of them) modified to not focus past infinity. I was adviced not to do this modification because termal variations is visible at infinity wide open. Astro photographers claim that the only way to ensure maximum quality under critical conditions is to focus directly on the film plane with a matted ground glass; focusing at where the lens stop at infinity won't solve anything. Granted, the differences is largest with longer lenses but it will still have an impact on fast, shorter focal lenght lenses. P�l
