[reh321]

Then I stand corrected. Is it the same for Canon ? I was under the impression they had changed the mount a number of times.

I don’t know about Canon’s history pre1985. Around 1985 they did make a dramatic change - basically retiring the FD-mount in favor of the EF-mount, making no effort to bridge the gap. To put this in Pentax context, the FD-mount was basically like the KA-mount, and the EF-mount is like the KAF4-mount. @Wheatfield; can give you the negative side of that. Personally, in 1995 I switched from Pentax to Canon because I so much liked the whisper silent operation of Canon’s usm/EF lenses. {I stayed with Canon until two of their Rebel bodies totally failed me in less than two years after each demonstrated symptoms of processor problems, and then I came back to Pentax}. I have now used Pentax K-30 and KP cameras, which combined have lasted as long as those two Rebels did; the K-30 does suffer from “Dark Image Syndrome”, but I use it now with old film lenses, mostly indoors with flash. So I still get some kind of service from the two Pentax cameras, while the two Canon cameras ended up in the town dump. Of course, recently, Canon has introduced two mounts, “EOS-M” cameras {which they now seem to be abandoning} and “EOS-R” cameras. In each case they {and others} sell adapters to fully use EF lenses on the new mount, although there is expectation that the adapters could stop functioning if that were convenient for Canon marketing. In DSLR’s, every DSLR works with every lens, if both were made after the switch.

Nikon does have an adapter so someone can use some of their DSLR lenses on their MILC cameras; I know that the lens must have an in-lens AF motor in order to AF at all, but I’m unclear about the rules. To me, they sound like “Old Mac’s farm” - “AI, AI, No”. In DSLR’s, I know with certainty, that some less expensive cameras won’t AF with some lenses - neither part has an AF motor.

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Last edited by reh321; 11-24-2022 at 09:45 PM. Reason: added DSLR-specific statements