On Tue, 29 Sep 1998 14:06:02 -0700, "ccrutcher" wrote:

>I have a couple of old lenses that I have used for years with an FM body. I
>recently bought an N90s and was wondering if these lenses will cause damage
>to the N90s. The manual for the N90s states that non-AI lenses should not be
>used. There in lies the problem. How do I tell if these are AI lenses? One
>lens, a 50/1.8 came with the FM. The other, a 135/2.8 I purchased
>separately. Both lenses have the old "horseshoe" indexing bracket, that the
>FM doesn't seem to use.

If they fit and metered properly on the FM without raising
the body AI meter tab, they are probably AI (well, the 50
f1.8 definitely is, since it was not made as a non-AI...).
OK, once more, THE EASY WAY TO TELL:
Run your finger around the rear edge of the aperture ring.
If you run into no ridges, the lens is NON-AI; if you run
into two raised ridges, the lens is AI... Non-AI lenses
can be modified to fit for about $30, including shipping,
by jtw3@aol.com (if my memory is correct...).