Canon EOS-1D X Mark III Advanced User's Manual page 829

C.Fn1
Exposure level increments
1/3: ⅓-stop, Exp comp ⅓-stop
Sets 1/3-stop increments for the shutter speed, aperture value, exposure compensation
amount, AEB range, and flash exposure compensation amount.
1/1: 1-stop, Exp comp ⅓-stop
Sets whole-stop increments for the shutter speed and aperture value, and 1/3-stop
increments for the exposure compensation amount, AEB range, and flash exposure
compensation amount.
1/2: ½-stop, Exp comp ½-stop
Sets 1/2-stop increments for the shutter speed, aperture value, exposure compensation
amount, AEB range, and flash exposure compensation amount.
Note
Display of the exposure level indicator is as follows when [½-stop, Exp comp ½-
stop] is set.
ISO speed setting increments
You can change the manual ISO speed setting increment to a whole stop.
1/3: 1/3-stop
1/1: 1-stop
Note
Even if [1-stop] is set, ISO speed will be automatically set in 1/3-stop increments
when ISO Auto is set.
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