Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 304)

k Shooting Movies
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The settable shutter speeds in the < s > shutter-priority AE and < a >
manual-exposure shooting modes vary depending on the frame rate of
the movie-recording quality.
Still photos cannot be taken during movie shooting. To take still
photos, stop the movie shooting and take still photos using viewfinder
shooting or Live View shooting.
Settable Shutter Speeds
Frame rate Settable Shutter Speeds
2 1/4000 - 1/125 sec.
3 1/4000 - 1/100 sec.
8 1/4000 - 1/60 sec.
7 1/4000 - 1/50 sec.
6 1/4000 - 1/30 sec.
5 B 4 1/4000 - 1/25 sec.
Still Photo Shooting