Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 300)

k Shooting Movies
300
Notes for < d >< s >< f ><bulb> Modes
You can lock the exposure (AE lock) by pressing the < A > button. After
applying AE lock during movie shooting, you can cancel it by pressing
the <
S > button. (AE lock setting is retained until you press the < S >
button.)
If you set the power switch to < 1 > and turn the < 5 > dial, you can set
the exposure compensation up to ±3 stops.
In the < d > and < bulb > modes, the ISO speed, shutter speed, and
aperture will not be recorded in the movie’s Exif information.
During movie shooting in the < d >, < s >, < f > or < bulb > mode, this
camera supports the Speedlite’s function to turn on the LED light
automatically in low-light conditions. (However, no icon indicating that the
LED light is ON is displayed on the information display screen illustrated
on page 305.) For details, refer to the EX-series Speedlite’s Instruction
Manual.