When a memory card is formatted in camera all files including photographs are marked for deletion and cannot be retrieved. Formatting also checks the suitability of a card for the camera. When taking a memory card out of one camera and put in another, check first there are no images on it and then format before further use, otherwise it may not function correctly.

Images can also be deleted individually, but they remain on the card! Space is made available for another picture, overwriting the image marked for deletion. If an image is deleted accidentally, the card should be removed immediately from the camera so that it can be recovered in a computer using special software.

It is not recommended that photographs are deleted whilst the memory card is in a computer as extraneous data can be transferred. However, formatting a card regularly in camera is good housekeeping, this ensures that the card is being used to its full capacity.

Do not use a memory card to store precious images permantly. If they fail, they do so without warning and it is a rather expensive way. If you have a computer consider storing images on CD or DVD in duplicate, or on an external high capacity hard drive.