Canon EOS-7D - K Protecting Images; Protect 

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Protecting the image prevents it from being erased accidentally.
1
Select [Protect images].
 Under the [3] tab, select [Protect
images], then press <0>.
 The protect setting screen will
appear.
2
Select the image and protect it.
 Turn the <5> dial to select the
image to be protected, then press
<0>.
 When an image is protected, the
<K> icon will appear on the screen.
 To cancel the image protection, press
<0> again. The <K> icon will
disappear.
 To protect another image, repeat step
2.
 To exit the image protection, press
the <M> button. The menu will
reappear.
K Protecting Images
Image protect icon
If you format the card (p.45), the protected images will also be erased.
 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.188), only the protected images will
remain. This is convenient when you want to erase unnecessary images
all at once.