Why ‘more megapixels!’ doesn’t mean better pix

When it comes to electronics, more is better. Consumers want more features, more hard-drive space, more cellphone minutes, and more battery life.

But with digital cameras, it’s not that simple. Many stores will tell you that the worth of a camera is measured in megapixels. The more manufacturers can pack in, the better – right?

Not necessarily, says Amit Gupta, founder of Photojojo.com, an online newsletter for camera tips and projects.

A high megapixel count doesn’t always equate to better image quality. In fact, if camera designers try to cram too many megapixels into a small camera it can actually have the opposite effect.

This counterintuitive snag mostly affects tiny digital cameras, the ones compact enough to fit in your pocket.

To keep sizes down, manufacturers place itty-bitty image sensors inside their point-and-shoot models. These small parts perform well within a certain range. But when companies try to raise the megapixel count without increasing the dimensions of the camera, that means the same size sensor now has to do more work.

This leads to larger but less accurate images, says Mr. Gupta. The overburdened sensor can lose sharpness, struggle in low-light situations, and add “noise” (small blotches or odd colors).

Digital SLR cameras are bulkier than sleek point-and-shoots, but the extra room allows for much bigger sensors and often better image quality per megapixel.

Cameras rarely advertise their sensor size, which makes this warning difficult to act on. But the problem usually pops up when companies release two very similar models, one with more megapixels and most likely a higher price. In those situations, the extra few hundred dollars doesn’t necessarily buy you a better camera.

Sensor technology improves all the time, making the issue of cramped megapixels less important each year. Improved lenses and anti-shake features also dampen the effect.

But even if companies could make a flawless 18-megapixel camera the size of a deck of cards, few people will ever need that much, Gupta says.

He suggests shoppers start looking at 8 megapixels, consider 10, but think hard before shelling out for a 12-megapixel camera or higher.

“Six megapixels is great for 8-by-10 prints,” he says. “We use a six-megapixel camera for everything on the site.... In fact, we’re making a Photojojo book and shooting with the same camera for all of those pictures.”