<p>As far as the Canon R (Canomatic) lenses are concerned, I managed to do some servicing on them myself. I repaired and cleaned a stuck aperture, fixed a bent aperture arm, removed some haze from inner lens elements and lubed a very stiff focusing ring. This on my so called Super-canomatic lenses 50/1.8, 35/2.5 and 135/2.5.<br>
To my experience, these lenses are very easy to open and, more important, to put back together again.<br>
On the other hand, I also have a Canonflex R2000 that needs servicing because the shutter times are way off. But doing that myself is way too complex for me.</p>