It is better to format your memory card rather than to delete images from your card no matter which type of card (CF I&II, SD, etc.) your camera accepts.
In your camera’s menu system you can find two possible options of removing photographs from your card: delete and format.
First of all, before deleting images or formatting a memory card make sure you have already backed up any important photographs by taking all the files off the memory card.
Secondly you need to know that by deleting images or formatting the card you do not lose the images even though you do not view the photos on your camera or computer. What you do is to remove any reference to the images. By using a card recovery tool it is possible to get the images back. You do not have this opportunity if a new image is written over the top of the old one.
Cameras automatically create folders/file structures where the images are saved. By deleting images you can delete one or more selected photos (or all) from their directories on the card, except the ones that may have been protected.
By formatting you replace the file structure including new directories and folders where photos are saved on the card. Therefore, the folder structure is re – organized. A lot of times we are using our card in different cameras. As a result new folders/file structures are created. In that case, not formatting may still leave some files, folders created by other cameras (even from the same manufacturer). That increases the risk of a corrupted card.
By formatting a memory card you prevent database errors and improve the overall performance of a card. It is a good idea to format it on a regular basis.