On Mon, 14 Sep 1998 22:56:42 -0600, "S Dong" wrote:

>A question regarding the telephoto lenses with drop in filters:
>
>Is it required to have the clear filter held in there to obtain the
>intended optical formula?

Not really - the only thing upset will be infinity-focus,
but that only slightly (and if it is an ED lens, it can
focus beyond infinity [neat concept! ;-], so the focus
error can be compensated for). BTW, these lenses often also
come with a gel drawer which can be used instead (when
using the gels, compared with the much thicker glass filters,
it is optically about like having no filter in place...).

>I believe a new lens comes with a set of filters (UV, red, etc?).
>Does one leave the UV one in the drawer?

Yes.

>Conversely, if one is buying a used lens, should they make
>sure a UV is in the drawer?

Depends on the price - the filter (and drawer) are not
terribly expensive.