Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 761)

Display Brightness
1.
Select [ : Disp. brightness].
2.
Make the adjustment.
Referring to the gray image, turn the < > dial to adjust brightness,
then press < >.
Note
To check the image's exposure, referring to the histogram is recommended ( ).
You can also access the screen in step 2 by pressing the < > button during
playback.
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