A friend of mine recently went shopping for a digital camera but walked out of the store empty handed. It wasn't that she couldn't find one; there were enough in the store to build a three-bedroom house entirely out of cameras.
The problem was that she was overwhelmed by the terminology and didn't feel she knew enough to make a smart choice. The little placards they put in front of the cameras on the store shelves use all sorts of terms not found anywhere else in the universe, like megapixel, ISO, and digital zoom. She asked me to make some sense of the alphabet soup of digital photography terminology for her. Here's the top five digital camera terms you need to understand when you go camera shopping.
Megapixel is the gold standard in camera jargon--it's the most important criteria to use when narrowing the field. Looking at megapixels first is kind of like going shopping for a monitor only after deciding whether you want a big LCD screen with a very high resolution--say, a 21-inch 1600-by-1200 model--or a smaller, lower-resolution screen, such as a 15-inch 1024-by-768 model.
Just as in our monitor example, the number of pixels you have will affect how big your final image can practically be. To get more specific, a camera's megapixel rating indicates how many millions of pixels the camera can record per shot. That capability, in turn, determines how large the picture can be printed and still look good. You should have at least 3 megapixels to make 8-by-10-inch prints, for instance. These days, cameras range from 2 to 8 megapixels; and I recommend avoiding the low end of the scale since it really limits your possibilities.
The acronym ISO refers to the International Standards Organization, which among other functions sets some standards for photography. When we talk about a camera's ISO settings, we're talking about ways to adjust how sensitive the camera is to light.
A digital camera's ISO rating corresponds to the speed ratings for 35mm film: A low number, such as ISO 100, is "slow," or relatively insensitive to light; a high number, such as ISO 400, is fairly sensitive. Every time you double the ISO, you halve the amount of light needed to properly expose a picture--and vice versa.
Unlike film cameras in which you must set the camera to correspond with the film's rating, the ISO of digital cameras is adjustable on the fly. To ensure plenty of flexibility, shop for a camera that has a good range: ISO 100 to 400 is typical in an affordable point-and shoot, and more expensive cameras allow you to use higher settings. Generally, you want to shoot with a low ISO because it results in a sharper picture with less digital noise; but a high ISO is handy for taking pictures at night and in the dark. If you want to do a lot of low-light photography, it's a good idea to look for a camera that has a wider ISO range. But as I mentioned, expect a significant amount of digital noise at ISO settings above 400.
Here's a spec you won't see advertised by the camera manufacturer: the time between when you press the shutter release and when the picture is actually taken. You'll need to read a camera review or try the camera in a store to get a sense of its performance in this regard.
All digital cameras suffer from some amount of shutter lag. Some cameras, particularly less expensive and older models, have insufferably long lag (an entire second or, in some cases, even longer). While few cameras have a shutter you might describe as instantaneous, better cameras feel almost immediate. I think it's important to experiment with a camera before you buy it to see if the shutter lag is going to be a problem for you.
Focal length is a measure of how much a camera lens can magnify a scene.
Terms like wide angle and telephoto describe the relative size of a camera's focal length. A short focal length like 20mm or 35mm is generally considered wide angle; it creates a wide, spacious view. Telephoto lenses like 100mm or 200mm zoom in on the action and include a very narrow field of view. As a point of comparison, the human eye has a focal length of about 50mm.
So how does all that add up when buying a digital camera? Simple: For technical reasons, it's a lot easier for digital camera makers to make long telephoto zoom lenses rather than to offer wide-angle lenses. But everyday photography--such as taking indoor photos, pictures of groups of people, and capturing wide scenes outdoors--often benefits more from wide angle than from telephoto capabilities. So look for digital cameras that offer a wide bottom end of the zoom range; you'll find it's more useful in the long run to get a camera that can handle 20mm wide angle rather than 400mm telephoto.
I usually recommend that digital photographers ignore the digital zoom feature entirely.
Here's why: Optical zoom uses the actual lenses to zoom in and out of a scene. Digital zoom, though, simply enlarges the pixels in the middle of the picture electronically and throws away the pixels around the edges. So digital zoom is essentially the same thing as cropping a picture in an image editing program.
You can usually disable the digital zoom feature by setting an option in the camera's menu, and that's what I do. Recently, a reader suggested one good use for digital zoom: You can crop your pictures "in the camera" so you can print without connecting the camera to a computer.