You can protect picture and movie files from accidental erasure by giving them protected status. After you take this step, the D5300 doesn't allow you to delete the file from your memory card, whether you press the Delete button or use the Delete option on the Playback menu.
You can also use the Protect feature when you want to keep a handful of pictures on the card but delete the rest. Rather than select all the pictures you want to trash, you protect the handful you want to preserve. Then you set the Delete menu option to All and dump the rest. The protected pictures remain intact.
Formatting your memory card does erase even protected pictures. In addition, when you protect a picture, it shows up as a read-only file when you transfer it to your computer. Files that have the read-only status can't be altered until you unlock them in your photo software. (In Nikon ViewNX 2, select the image and then choose File-->Protect Files-->Unprotect.)
Remember, too, that locking the file prevents you from assigning a rating to it — so rate photos before giving them protected status.
To protect a file, take these steps:
Display or select the picture or movie you want to protect.
In single-image view, just display the photo or movie.
In 4/9/72 Thumbnail mode, use the Multi Selector or Command dial as needed to place the yellow highlight box over the file's thumbnail.
In Calendar view, highlight the file thumbnail in the strip of thumbnails that appears on the right side of the screen. (Press the Zoom Out button to jump between the calendar dates and the thumbnails.)
Press the AE-L/AF-L button.
See the key symbol to the right of the button? That's your reminder that you use the button to lock a picture. A key symbol also appears with locked photos during playback.
To remove protection, display or select the image and then press the AE-L/AF-L button again.