I want to get an older body such as the EOS 620. Do newer lenses autofocus with older bodies? Are there compatibility issues between generations like Nikon?
With Canon, if it fits, it works. I've used old lenses with newer un-nameable bodies, and newer lenses (eg 40 STM and 70-300L) on older bodies with no problems either way.
The biggest incompatibility is with older 3rd-party lenses (like Sigma & Tamron) on the newer digital bodies, but I've never heard of any problems with newer lenses (of any brand) on older bodies.
I want to get an older body such as the EOS 620. Do newer lenses autofocus with older bodies? Are there compatibility issues between generations like Nikon?
All I can say is that my EOS 50e flawlessly works with any very very later (recent) lens even with an IS lense.
I am amazed and it is unbelievable but true, seems canon do know how to manage design and production for compatibility.
I want to get an older body such as the EOS 620. Do newer lenses autofocus with older bodies? Are there compatibility issues between generations like Nikon?
As mentioned above, yes: all EF lenses will work on even the first EOS cameras such as the 650 and 620. You will not want EF-S (those are for Canon crop-sensor digital cameras), nor do you want EF-M (intended for mirrorless digital).
So, from 1986 onwards to today, there are no compatibility issues between EF lenses and Canon EOS bodies (either 35mm or digital full frame). You can use old EF lenses with new bodies or new EF lenses with old bodies.