Camera OFF while Mounting / Dismounting Lens If certain lenses are removed from the 5D Mark II while it is turned on, their iris setting may be misread by the camera when they are reinstalled. (This issue is unrelated to the VAF-5D2b, and can happen even if the VAF-5D2b isn't being used.) The power on/off instructions included below will ensure that this doesn't happen. If you inadvertently remove a lens with the camera on and cause this to occur, the solution is just to manually adjust the camera iris control to fully open the lens, and then to re-adjust it to your desired f-stop.
Avoid Touching Optical Surfaces As with all precision coated optics, fingerprints and smudges on the VAF-5D2b can degrade image quality, and can be challenging to remove completely (especially when you're in a hurry.) When handling the VAF-5D2b, be extra careful to avoid touching its optical surfaces.
Live-View Timeout Whenever you press the "Live-View" button to raise the 5D Mark II's reflex mirror, the camera initiates a time-out cycle, which will close the shutter and drop the mirror after a finite interval of time. This interval is usually about 2 minutes, but can be much shorter in certain circumstances – for example if the camera is hot, or if its battery is low on charge. Make sure to install the filter assembly without delay after you press the "Live-View" button.