Resolution. The higher the resolution of a digital photo, the larger it can be displayed or printed without degrading the image quality. While image editing software will allow you to blow up or reduce pictures, the quality starts to suffer immediately -- particularly with enlargements. Look for a resolution of at least 640 by 480 pixels for serious work. If you need absolutely top quality for professional reproduction, you're still better off with a film camera and a scanner.

File format. 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.

Compression. Digital images can occupy huge amounts of memory and disk space. So developers have invented ways to compress them. The most common standard is a product of the Joint Photographic Experts Group -- JPEG for short. 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. If you can afford it, get a camera that lets you decide.

Speed. Digital cameras are slow, period. They can take anywhere from five seconds to half a minute to store each picture once you've pushed the shutter button. So don't expect to take rapid-fire sports shots. On the other hand, five seconds is a lot better than half a minute if you're taking candid photos or have people waiting for you to shoot their pictures. If speed is important, choose a camera that processes photos quickly.

Battery life. Digital cameras eat batteries alive. Some cheaper models will only accept disposable single-use batteries, and these may only last for three or four "rolls" of digital images. This can get very expensive. Look for a camera with a rechargeable battery. Better yet, get one that can be recharged while it's in the camera. Best of all -- a camera that accepts either rechargeable or single-use batteries. That way you can always carry spares.

Ergonomics. There are some weird-looking digital cameras out there. Some designs make it easier to take pictures, others make it harder. A major issue is the viewfinder -- or lack thereof. Some camera makers omit the traditional viewfinder altogether in favor of an LCD screen on the back of the camera. But instead of holding the camera up to your eye in the time-honored fashion, you'll have to hold it about a foot in front of your face to see what you're taking. This may not be comfortable for bifocal wearers, and it's harder to hold one of these cameras steady. Always try the camera out before you buy (you won't be wasting any film). Also, look for a shutter and other adjustment buttons that are easy to find. It's no fun fumbling when you should be concentrating on composing your pictures.

Photo capacity and extra storage. If you're going to spend a day shooting with a traditional camera, it's easy to buy four or five rolls of film ahead of time, or find more if you run low. But a digital camera's storage capacity is finite. Once you've filled it, you have to transfer your images to a computer before you can start snapping again. Unless you're traveling with a laptop computer, this can be a problem. So it's a good idea to buy extra memory cartridges. For serious photographers, more storage is always better.

If you use a desktop computer, you're probably better off with a camera that stores images on compact flash memory cards. These are available in most computer stores and many photo shops. Laptop users may prefer cameras that use PC cards that fit into the slots in the side of laptop computers.