Canon EOS-1D X Manual (en)

Enlarging and Viewing an Image in the Preview Window
The preview window appears.
Click the [
] in the Upper left of the preview window to close the 
preview window.
Preview window
Tool palette
By selecting the [Preview] menu 
 [AF points] in the preview 
window, you can display the AF points selected in the camera at 
the time of shooting. However, AF points are not displayed for 
images whose image size has been changed and then been 
converted and saved 
, images for which you selected an 
effect other than [Shot settings] as correction of fisheye lens 
distortion aberration, or images which have had settings specified 
during RAW processing on the camera for distortion correction or 
chromatic aberration correction.
Click the area you want to enlarge.
The area you clicked is enlarged to 100% (actual pixel size).
Click again to revert to the full view.
To change the display area drag on the image.
Enlarging and Viewing a Specific Area
Select any enlargement ratio from the [Preview] menu.
To display an image in an enlargement ratio other than 100%
While in the preview window, you can select the [Preview] menu 
[Preview control panel] to use various preview functions. For details, 
see “Checking an Image Using the Preview Control Panel”