Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 449)

Specifying the Range of Images to Protect
While looking at the images in the index display, you can specify the first and last images for
a range to protect all the specified images at once.
1.
Select [Select range].
2.
Specify the range of images.
Select the first image (start point).
Next, select the last image (end point). The images in the specified
range will be protected and the <
> icon will appear.
To select another image to protect, repeat step 2.
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