In article <4c0pvt$6jh@netnews.upenn.edu>, Peritt_d@a1.mscf.upenn.edu says...
>could someone tell me what A1 is and what other classifcations for >nikon lenses are. I am sorry for the naive question.

No problem. If you have an older camera that requires the clip on
the lens at f5.6 for meter hook-up (if there is no clip, stop-down metering works fine), you may want the lenses with the clips: non-AI, AI, and AIS (these are the manual, all-metal lenses in the line).
If you have a newer camera that requires the ridge at the back of
the lens aperture ring for meter hook-up (some bodies allow you to
flip up the AI body tab and use stop-down metering with non-A.uto-I.ndexing lenses), you may want A.I. lenses: AI, AI'd
(with the ridge cut by yourself, or someone like John White), AIS (orange minimum aperture, scoop out of flat surface on the flat rear
of the chrome bayonet mount - enables some metering features on a few cameras), E (AIS, but was a less expensive series in the Nikon line), Auto Focus (which is also AIS), and P (which is AIS, but with AF electronics added [rare]). The metal clip at f5.6 may be added to AF lenses (and, with more difficulty, to E lenses) to make them a bit easier to use with older bodies' meters. Since Nikon tries to keep
new and old equipment compatible, most of the designations are not
of great importance practically speaking, except for AI vs. non-AI
(don't try to put a non-AI lens on an AI body, unless you know how to
do it).
Hope this helps.