On a conventional camera you get one picture in each frame of a roll of film. A 24-shot roll gives 24 shots regardless of the quality of each picture. This can be anywhere from four images at the highest quality setting to 40-plus at a lower resolution. Other important factors to consider are how big the removable memory card is, and how good the lens is. A fixed focus lens can give blurry edges on long shots.
Most digital cameras save images to a removable memory card.
The number of shots you can squeeze onto each card depends on the image resolution and degree of compression. The average memory card size is about 8Mb, which can hold up to 40 reasonable quality shots. Drive to move images from the memory card onto a matchbox-sized 40Mb disk. If you are tempted by a camera that has only an LCD screen viewfinder, be prepared for two things. First, it will be hard to see through it in Australian sunlight, and second, it will flatten the batteries big time.