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
it might not be a bug, macro lenses change aperture with focus because the extreme focus change actually changes the length of the lens. since an F stop is calculated by dividing the physical opening size into the focal length (which has increased dramatically with close focus) then we can expect a change in the aperture displayed.
the early 50mm micro nikkors used to correct for this by opening up the aperture with focus change
The wrong point here is that most people on this topic was talking about a complete different thing and didn’t understand the reports (we encourage to read the original one again, and check the updated information at the blog)
We are reporting an “iris jitter” issue, an abnormal behavior of the iris while changing focus in some lenses (in the full manual movie mode), NOT a variation of the aperture (real or non real value) while focusing to macro or something like that.
These video tests are very clear: http://5dmark2.wordpress.com/2010/04/08/malfunction-in-firmware-2-0-4-update/
People should see them and read the reports carefully to understand what the issue is really about.
This is is a firmware issue, not a lens issue. And it also affects some non-Macro lenses (Canon and 3rd party ones)
As we wrote in our last blog post, Canon seems to be aware of this issue now.