There are settings within the camera(s) that allow you to choose the quality of the photos. the higher the quality the better the photo and the larger; therefore the fewer number that can be placed on your card. Carry an extra card as memory these days is a good bang for the buck. It also ensures that you have the photos saved after the dive should something occur to the camera during the following dives.
Just my .02cf worth and Best FIshes!!! [