Thank-you for your question.
Generally and in basic terms, when you format your memory card you
write to every spot on the card therefore removing all traces of what
was on there previously. When you "delete all" from your card you are
only removing the information that tells your card reader where to
find your pictures on the card.
In theory, if you were to need to recover lost data from your card it
would be impossible in the first case but it might be possible in the
Additionally, there is the possibility (although very very remote)
that you could wear your card out if you formatted it every time.
Every card has a finite lifetime and it is measured by how many times
you can write data to the card, the good news is though that the
number of "writes" you can make to the card is usually in excess of
On the flip side, if you "delete all" every time there is a small
possibility that the filing system on the card will be corrupted when
you transfer the data to your PC (for instance if you used your PC
instead of your camera to delete an image).
Another consideration is on many cameras it is often quicker to format
a card than to delete all the images on the card.
In summary, I approach the matter this way - if I am absolutely sure
that I do not need the pictures again I will format the card. If
there is even the remotest possibility I might need to recover the
pictures I will "delete all". If I am to take an important set of
photographs I will format the card. If I was to sell the card I would
use the format function.
I hope this answers your question. Should you require any further
assistance on this subject please do not hesitate to ask for
Some discussion on this matter: