Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 213)

Multiple Exposures
Merging Multiple Exposures with a RAW Image Recorded on the Card
Checking and Deleting Multiple Exposures During Shooting
You can shoot multiple (2–9) exposures to merge into a single image. In Live View shooting,
you can see in real time how the exposures are merged when you shoot multiple-exposure
images.
1.
Select [ : Multiple exposure].
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