How to control the 5D Mark II’s aperture

As I mentioned in my previous post about controlling the 5D Mark II’s shutter speed for video, it seems that the auto metering likes to use a shutter speed that is 1/focal length. It turns out that you can also exploit this behavior to get some control of the aperture.

If a scene is too bright, the 5D Mark II will stop down the lens before it drops the shutter speed below 1/focal length. So if you are working with a zoom lens, you can force a smaller aperture by zooming to a longer focal length until the camera picks your desired aperture. Then lock the exposure with * and zoom back to the actual focal length you want to use.