Canon Rumors is reporting this could be considered “Normal” behavior for this lens. I will follow up with more details when available.
The crew over at 5D Mark II Team have discovered a glitch in the new firmware update 2.0.4 for the Canon 5D Mark II. The Canon 100mm Macro’s Iris takes on a life of it’s own. Check out the tantalizing video of the Iris acting up. Here are some additional details from the 5D Mark II Team’s website. Click Here For More Details.
· It does NOT happen with Firmware version 1.1.0 .
· It happens WHEN recording video and also when NOT recording video .
· It happens with ISO and every possible automatic setting fixed to a value, or turned off .
· It happens in C1/C2/C3 too (if they are registered as “M” modes for movie recording) .
· It happens in PAL and NTSC modes .
· It happens in both lens modes: MF and AF mode .
· The camera does NOT tell any change in aperture setting (it keeps showing the same value) nor give any kind of advice either .
· The iris shifting can be heard (and seen) .
· The brightness shifting of the image is visible on the camera’s LCD monitor when the iris/aperture shift occurs .
· The iris/aperture usually changes in small values, but enough to make the footage unusable, so using this great lens for movie/video purpose may result impossible