Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 179)

Auto Lighting Optimizer
Brightness and contrast can be corrected automatically if shots look dark or contrast is too
low or high.
1.
Select [ : Auto Lighting Optimizer].
2.
Set a correction option.
Caution
Noise may increase and apparent resolution may change, under some shooting
conditions.
If the effect of Auto Lighting Optimizer is too strong and results are not at your
preferred brightness, set to [
Low ] or [ Disable ].
If a setting other than [ Disable ] is set and you use exposure compensation or flash
exposure compensation to darken the exposure, the image may still come out
bright. If you want a darker exposure, set this function to [
Disable ].
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