Canon EOS 90D DSLR Camera with 18-135mm Lens - Manual (Page 514)

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Adjusting the Screen Brightness
1 Select [ 5 : Disp. brightness].
2 Make the adjustment.

Referring to the gray chart, use the <
Y
>
<
Z
> keys to adjust the brightness, then
press <
0
>.
o To check the image’s exposure, referring to the histogram is recommended
( = 389).