I have a friend who is pro photographer . He is using his old EF 24-70 f/2.8 on EOS R , with an adaptor (the original) . The lens stopped working and at the shop of his technician , the technician told him , that it's very common with ef lenses on adaptor. Could it be true ? May the EF lens on RF mount is straining more than on native mount and breaks more soon ?
Yes, it’s a little known fact, but it’s true. However, it doesn’t apply to all EF lenses; all the STM-equipped models are fine, as are most of the post-live-view-era USM drives. The problem is that the older drives weren’t really optimized for back-and-forth focus racking in small increments, which is something that mirrorless cameras do more often.
Let me say though, that your pro friend probably uses the hell out of his lenses, and it sounds like he shoots in low light situations a lot. Because that’s usually the only scenario in which Canon mirrorless cameras use hybrid AF (both phase and contrast detection). With normal, amateur use, this shouldn’t be a problem at all.
And before people start grilling me - I know this from the Olympus Four Thirds days (the old DSLRs). Lenses not optimized for live view sucked in that mode, and if the user wasn’t cautious, the AF motors would fail much earlier because of the constant racking. The problem became even worse when those lenses were adapted to Micro Four Thirds cameras without OSPDAF, as those would drive them to hunt even more rapidly and constantly. Similar problems have been reported with Sony mirrorless cameras with A-mount lenses, or adapted EF ones.
