When mirror clearance happens, does it cause any permanent damage, say, scratch, to the rear element of the lens and/or reflecting mirror of the camera? For example, Zeiss Distagon 21mm f2.8, Leica Super-Elmar-R 15mm f3.5. I am using a 5D. Thanks.
Most rear cells have a flange which the mirror will hang up on rather than the glass itself. If you do get glass on glass contact, however, you will nick coatings quite quickly. Certainly it does your camera no favour to have its mirror repeatedly wedged to a stop at a point other than fully up or fully down, either, and both the viewfinder fidelity and the AF system could suffer in time.
Manufacturers (one in particular, really, thanks to its shortest-in-class register) must consider this all an annoying support headache. It's a wonder they don't humour everyone with a slightly shorter, or more inset, mirror. On the bodies that don't demand 100% viewfinder coverage this shouldn't be very hard to implement, and I can't imagine alt-glass will ever really cut into new lens sales significantly.
Any one tried these two lenses on 5D2?