« on: April 10, 2014, 07:56:16 AM »
On topic ... I sold my EF 40mm f/2.8 STM lens because it backfocused. This was apparently within specifications and I was told to upgrade my cameras to AFMA-enabled models to solve the problem.
Sounds like you've been unlucky; most people seem to report very little MA needed on the 40 pancakes. The AFMA enabled models have completely changed my attitude and needs in lenses. Before, the quality of the manual focus mechanism on a lens was very important to me. Now with AFMA and BBF I basically don't use manual focus anymore, and so I'm using cheaper versions of lenses than I once would have done. Even when zone focusing I use AF. The only exception would be when focusing for a specific distance that is covered by the lens's distance scale.
I've had non AFMA cameras such as the 5D that have been fine until the body has suffered a good heavy knock or drop. Then the critical focus on a fast lens is out.
The irony of it is that these DSLR bodies are highly resilient to physical abuse, but an impact can shift the position of the AF module enough to cause problems.