Nikon D300 User Manual page 50

Figure 2-6. Hide image screens – Deselect All? option
Note: If you unhide images that are both hidden and
protected, the protection is also removed at the same time.
You protect/unprotect an image by displaying it on the
Monitor and then pressing the Protect button, which is
marked by a key symbol on the back of the camera (next to
the question mark).
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