Why increase pixel counts?

There are advantages to increasing the number of megapixels, experts say, but there are costs too.

There are advantages to increasing the number of megapixels. Larger prints that require a minimum pixel count can be easier to make and consumers can crop images to focus on just the subject matter they want.

But there are costs, too. Among the more obvious burdens: camera image-processing chips have more data to digest, memory cards and hard drives fill up faster, and photo editing puts greater space, memory and time demands on computers.

More subtle problems also are possible. Camera image sensors rarely get larger from one generation to the next, so squeezing more megapixels out of a sensor means each pixel on the sensor is smaller. In most of the chip business, smaller electronics are dandy, but with cameras, they translate to less light per pixel.

That light difference means it's harder to distinguish the signals produced by light from the electronic noise in the sensor. The idea of making the signal-to-noise ratio worse may sound pretty technical, but possible consequences are easily understood: images suffer from color speckles and cameras work poorly in dimmer conditions such as indoors.

"If you try to cram more pixels into the same amount of space, you risk getting signal degradation because you're not getting as much light into the same pixel," said Chris Crotty, an analyst with iSuppli.

It can be tough for consumers to understand why they might not want to snap up the most megapixels possible. "People can understand the idea of more numbers is better," Crotty said. "But signal-to-noise, fill factors, dynamic range, blooming--these are concepts most people aren't going to understand."

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