Nikon's failure . . .

Started Aug 19, 2006 | Discussions thread
avidday Senior Member • Posts: 2,082
Nikon meter coupling.

David Martin wrote:

Perhaps I've misunderstood, but I thought the D80 cannot meter at
all with AIS lenses?

No you haven't misunderstood that - the D80 (or D50 or D70 or D100 and most of the final generation of low end and mid range autofocus 35mm film bodies) don't meter with AI-S lenses. The lenses will index to the shooting aperture automatically, but metering is inoperative.

What you have misunderstood, however, is that the sort of metering you are talking about with the the 350D - stop down metering - is essentially unknown on Nikon SLR cameras going all the way back to the original Nikon F. As long as Nikon SLRs have had meters, they have been aperture coupled (even before the introduction of TTL metering). This was originally done via the characteristic coupling yoke on the aperture ring, but since 1977 it has been done via the Automatic Indexing (AI) system. AI and AI-S lenses have additional two mechanical couplings which communicate the selected aperture (a coupling ridge on the aperture ring) and the lens maximum aperture (via an indexing post). The D200/D1/D2 family have a mount which includes these couplings and can meter. AI-S support requires a more complex lens mount and a parallel electro mechanical coupling to the cameras exposure meter. It isn't cheap and it's exclusion certainly isn't a marketing decision. And it certainly isn't something which the EOS 350D supports.

And, of course, the only reason why Canon EOS mount cameras support stop down metering is to provide a semblence of backward compatibility with long abandoned FD mount. Pick you poison - lenses which only fit via an adaptor, require transition optics or can't focus to inifinity, don't index, but the camera can meter, or lenses which fit without an adaptor, are optically fully compatible, index automatically, but don't meter.

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