As far as I was aware Canon hadn’t actually acknowledged the erratic aperture behaviour issue on the 550D and 1DmkIV up till today. I’ve found with my Canon 100mm macro and 200mm f2L the aperture has been jumping quite a bit as you focus in and out. Hopefully this latest firmware will fix this permanently. This from the Canon site –
The following fixes have been incorporated.
Fixes a phenomenon in which the set aperture moves unexpectedly when shooting movies in manual exposure mode using some Canon lenses (such as macro lenses).
Supplemental Information: This phenomenon involves the aperture of the lens moving unexpectedly when the focusing ring moves (during focusing). Please note that aperture values also change when operating the zoom ring of a zoom lens that has variable maximum aperture values; however, this is a normal operation because the camera controls aperture values properly depending on the focal length (zoom position).
Corrects misspellings in the French and Spanish menus for applicable products.
How do I check the camera’s current firmware version number?
Turn the Power Switch
, and press the