Permanently delete images from a memory card
Despite what the camera manual says, when you erase images from a memory card, they aren’t really gone. Even when formatting a card, some of the content may remain.
Generally, this is a good thing. If you erase images by mistake, there is a good chance of recovering them with image recovery software, if the memory card hasn’t been corrupted.
Still, there are times you may want images totally removed from a card.
Overwriting files on a memory card
Image and video files can still be recovered until they are overwritten. According to developers at Art Plus, to ensure no one is able to read or recover deleted images, “format the card in your camera and then shoot random images until the card is filled again. Earlier images will be rewritten by random ones.”
Some digital cameras have a special Low Level Format option that erases more data on a card than a standard format. While low level formatting takes slightly longer than regular formatting, it is good practice do do a low level format now and then. Still, some images may not be completely removed from the card unless you use the process mentioned above.
Wiping a memory card clean
There is also software, such as SanDisk’s RescuePRO that completely wipes/deletes data from memory cards. Because of the complexity of the process, wiping a card can take a very long time.
A word of caution
Before wiping or overwriting files, make sure that’s what you really want to do. There is no way of recovering files once a wipe has been done or files are overwritten by new files.