Companies making digital cameras seem anxious to repeat the mistakes of the folks selling personal computers. Where PC vendors trumpet clock-speed measurements, camera manufacturers push megapixels, the millions of tiny dots than make up the resolution of the photo.

Years ago, when the two-megapixel images created by mid-range models couldn't always yield a good 5-by-7 print, it made sense to focus on this number. But times have changed. Even today's cheapo models capture three megapixels of detail, and four- and five-megapixel resolutions -- good enough for 8-by-10 prints -- are commonplace.

The industry would now like to sell you six-, seven-, eight- or 10-megapixel cameras. But unless you want poster-size blowups or you crop your shots with a chainsaw, those higher-resolution photos will not look any better on a screen or a wall. They'll just take up more space in your camera and on your hard drive.

For somebody looking to take mostly candids and snapshots, three to four megapixels are fine. Those who spend more time composing shots and who might like big prints of the results will need five to six megapixels.

The other number cited in most camera ads is its zoom factor, or how close its software and lens can get you to a distant subject. Ignore the number for software, or digital zoom -- it's no different than cropping a photo to enlarge the subject. The optical zoom generated by the workings of a camera's lens is what matters. A 3x optical zoom is routine; cameras with more than a 5x optical zoom won't fit in the average pocket.

Then consider the type of memory card a camera uses. Of the four major, incompatible formats -- Compact Flash, Memory Stick, SD Card, xD-Picture Card -- SD Card is the most popular and is one of the smallest and usually cheapest types of card. Compact Flash is second-best; although these cards are larger, they tend to hold the most data, making them widely used in high-end models.

The last data point to ponder is the hardest to find. It's the "shutter lag" between the click of the button and the capture of the photo. Although this delay has greatly been reduced in most cameras, it can still bother people who are used to film cameras and unfamiliar with tricks to minimize it, such as focusing on a photo's subject ahead of time.

You'll have to look up this number at the camera manufacturers' Web sites, assuming they list it at all. Kodak provides three different lag measurements, but Canon, Nikon, Olympus and Sony only report how many pictures per second their cameras take in continuous-shooting modes. (Reviews at camera-enthusiast Web sites -- for instance, and -- do report these figures.)

The rest of camera shopping consists largely of finding one that suits a user's picture-taking style. Somebody who takes a lot of snapshots will probably want a camera with a simple interface that makes it quick to switch among preset shooting modes. But a photographer who composes each shot will probably need one that provides manual control of aperture, exposure and other settings.

The most artistically-inclined photographers will probably be happiest with a larger, costlier digital single-lens-reflex (D-SLR) model that offers the same exact control and fast operation of a film SLR.

When you've narrowed the choice down to a handful of models, two factors can break a tie. Cameras that take standard-sized AA or AAA rechargeable batteries will be cheaper to operate than those requiring proprietary batteries. And bigger displays for inspecting shots are also better, provided the camera also includes a traditional optical viewfinder.

Do yourself a favor and go to the retail store to put the cameras through a touch-and-feel session. There's no substitute for picking up a camera, touching the buttons and judging the on-screen controls for yourself.

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