Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 163)

2.
Select the desired image size.
Turn the < > dial to select the image size.
Both RAW and JPEG images will be captured when / and
/ / / are displayed together.
Both RAW and HEIF images will be captured when / and /
are displayed together.
Turn the < > dial to select the card for recording and playback
( ).
Note
To set separate image sizes for each card when [ Record func. ] in [ : Record
func+card/folder sel. ] is set to [ Rec. separately ] ( ), turn the < > dial, select
a card, and set the image size.
“Image quality” in this guide refers to both image size and JPEG/HEIF quality (
).
HEIF can be specified when [ HDR shooting ] in [ : HDR PQ settings ] is
set to [ Enable ]. You can convert these images to JPEG images after shooting ( ).
Setting size via the menu
1.
Select [ : Img type/size].
The screen displayed varies depending on [ Record func. ] settings
in [ : Record func+card/folder sel. ].
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