A related quality to look for when buying a camera is image sensor "sensitivity." The difference between a camera that maxes out at ISO 400 and one that goes up to ISO 1600 is the difference between night and day -- literally. At higher ISO settings, you can take pictures of darker scenes without any flash at all, which provides a more natural, more evenly illuminated shot.

The speed at which you can set these lighting options can mean the difference between capturing a great shot or missing it.

Bad timing. By definition, photographs capture an instant in time. Say something amazing, funny or unusual happens right in front of you. How long does it take to turn on your camera and take a picture of it? How long to auto-focus? How long to take the second and third picture? And what will you miss while you're waiting for your camera?

If your digital camera is slow -- as most of them are -- you could miss the best shot.

Have you ever seen professional photographers work? They usually take an enormous number of pictures quickly. The reason is obvious: Taking more pictures increases your chances of capturing just the right moment.