Digital camera makers use a variety of schemes to store pictures. Some use their own, proprietary format to store images and provide software that will convert them to industry standards such as JPEG or TIFF files. Some use the JPEG format from the start, while still others have switched to a new FlashPix format developed by Kodak, Hewlett-Packard and other industry giants. If you're in doubt about this, look for a camera that can store images on your hard disk in JPEG or TIFF format. Virtually all graphics programs can use these files without further conversion.
Digital images can occupy huge amounts of memory and disk space.
So developers have invented ways to compress them. The problem is that the more a JPEG image is compressed, the more detail and color fidelity it loses. Some cameras use maximum compression to make room for more photos. Others give you a choice of compression ratios. With lower compression, you'll be able to store fewer images, but the quality will be higher.