In article <177B113F0AS85.RWALTON@UNIVSCVM.CSD.SCAROLINA.EDU>, RWALTON@UNIVSCVM.CSD.SCAROLINA.EDU says...

>I have a Nikon FM, and while it accepts older, Non-AI lenses,
>I was told it will only meter using the "stop-down" technique....
>Could somone please explain this? Thanks...

The Nikon FE, FM, F3, and F4 allow the small body tab that contacts
a ridge on AI (Auto Indexing) lenses to be flipped up out of the way
so that non-AI lenses will fit without AI modification. Once this is
done, moving the aperture ring has no effect on the camera meter.
It is necessary to push the DOF button/lever to close the lens
diaphram to the selected f-stop (or any fraction) while taking a
meter reading. This can be done with AI lenses, also, and has the
slight advantage of taking the meter reading at the actual aperture,
and not at the camera-simulated aperture (which is normally done
with AI metering, so that the lens diaphram can remain open for bright
viewing, regardless of the aperture selected), which can have some error.
If the lens is well stopped-down, stray light entering the viewfinder
can affect the meter reading, so shield the finder eyepiece while
metering.
Hope This Helps