Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 488)

3.
Select the desired image size.
Press < > to display the image sizes.
Select the desired image size (1).
4.
Save the image.
Select [ OK ] to save the resized image.
Check the destination folder and image file number, then select [ OK ].
To resize another image, repeat steps 2 to 4.
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