Canon EOS 5D Mark III Instruction Manual (en)

K Protecting Images
You can protect all the images in a folder or on a card at one time.
Under [31: Protect images], when 
you select [All images in folder] or [All 
images on card
], all the images in the 
folder or on a card will be protected.
To cancel the image protection, select 
[Unprotect all images in folder] or 
[Unprotect all images on card].
During image playback, you can use the <c> button to protect an 
Set [53: 
btn function] to 
Play back the images and select the 
image to be protected.
When you press the <c> button, 
the image will be protected and the 
K> icon will appear at the top of 
the screen.
To cancel the image protection, press 
the <c> button again. The <
icon will disappear.
 Protecting All Images in a Folder or Card
Set with the <c> Button
If you format the card (p.53), the protected images will also be erased.
Movies can also be protected.
Once an image is protected, it cannot be erased by the camera’s erase 
function. To erase a protected image, you must first cancel the protection.
If you erase all the images (p.284), only the protected images will 
remain. This is convenient when you want to erase unnecessary images 
all at once.