Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 511)

HDMI HDR Output
You can view RAW or HEIF images in HDR by connecting the camera to an HDR TV.
1.
Select [ : HDMI HDR output].
2.
Select [On].
Caution
HDR display in HDMI output is not available for RAW images captured with [ HDR
PQ settings ] set to [ Disable ].
Note
Make sure the HDR TV is set up for HDR input. For details on how to switch inputs
on the TV, refer to the TV manual.
Depending on the TV used, images may not look as expected.
On HDR TVs, some information may not be displayed.
Quick Control RAW processing of displayed images is recommended if you will
process RAW images while viewing HDMI HDR output.
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