Nikon Z 7 Reference Manual page 352

4
Compare the copy with the original.
The source image is displayed on the left, the retouched copy
on the right, with the options used to create the copy listed at
the top of the display. Press 4 or 2 to switch between the
source image and the retouched copy. To view the
highlighted picture full frame, press and hold the X button. If
the copy was created from two source images using Image
overlay, or if the source has been copied multiple times,
press 1 or 3 to view the other source image. To exit to
playback, press the K button, or press J to exit to full-frame
playback with the highlighted image displayed.
D
Side-by-Side Comparison
The source image will not be displayed if the copy was created from a
photograph that was protected or has since been deleted.
328 Menu Guide > N The Retouch Menu
Options used to create copy
Source image Retouched copy