Canon EOS 5D Mark II Instruction Manual page 228

Troubleshooting Guide
During movie shooting, the exposure becomes bright
momentarily.
Changing the aperture during movie shooting is not recommended
since changes in the exposure, due to the drive of the lens aperture,
will be recorded.
If you use a lens whose aperture changes while you zoom, you should
not zoom while shooting a movie. Zooming while shooting a movie
may record changes in the exposure.
When the movie is played, the subject looks distorted.
During movie shooting, if you quickly move the camera left or right
(high-speed panning) or shoot a moving subject, the image might look
distorted.
When I shoot still photos during movie shooting, movie
shooting terminates.
To shoot still photos during movie shooting, using a CF card
compatible with UDMA transfer rates is recommended.
Setting a lower image-recording quality for still photos and shooting
fewer continuous still photos can also resolve the problem.
The movie cannot play.
Movies shot with another EOS camera might not play on this camera.
Movies edited with a personal computer using the provided software,
etc., cannot be played with the camera.
When the movie is played, camera operation noise can be heard.
If you operate the camera's dials or lens during movie shooting, the
operation noise will also be recorded. Using an external microphone
(commercially available) (p.141) is recommended.
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