From 5D Mark II Team
Description of the problem:
When a Canon EF 100mm f/2.8 Macro USM lens is mounted on the camera and the user manually changes focus (rotates focus ring), the lens changes the iris/aperture “by itself”, even when the camera is in full manual mode.
It is not normal, and should not happen. The tests were made by several users with many copies on many camera bodies, so it’s not an isolated lens problem.
▪ This malfunction always occurs in this situation:
When the camera is set to M (Manual) mode and in Live View mode (Still+Movie – Movie Display), which is the correct mode for “full manual control” in movie mode.
Read more about the issue below.
thanks everyone that sent this in