In article <01bc2aa2$735d63a0$f24c2499@sualocin>, Enyo@bigfoot.com says...

>I use to use a 1000mm F11 Nikon and it was designed to focus past infinity.
> The reason was so you could focus with IR film. Some of Nikons other
>lenses (in the old F1 days) also allowed focusing past infinity. I think
>for most uses this 'feature' is more of a problem than a 'benefit'
>(thinking of all the soft pictures I took during the day). At f4.5 the
>depth of field is enough I doubt you could do better by hand focusing
>unless there is a problem with the lens.

Hmmm, Mirrors and ED-type lenses focus beyond infinity to allow for
changes in FL with temperature change, not to allow for IR focus
(One focuses *away* from infinity-focus for that...). Non-ED lenses
did not need to focus "beyond infinity" (neat concept! ;-), so they
are made to stop just at infinity focus (with luck! ;-). BTW, making
the lens focus beyond infinity is a rather easy adjustment, though
the footage scale would then be a bit off without a bit of minor
machining to an internal part...
Hope This Helps