By now you hopefully know that more megapixels don’t necessarily make a better camera. For one thing, you can almost double the megapixels of a camera while only gaining about a 40% increase in resolution. For another thing, it takes a lot more than just sheer number of pixels to produce a decent image. Nevertheless, point-and-shoot cameras with ginormous megapixel stats (now topping 12 MP) continue to hit the market. But Ross at Petavoxel says there’s another reason to avoid huge MP point-and-shoot cameras: something called the Airy disk.

At microscopic scales, the wavelike nature of light makes it act in a slightly “squishy” way. Points of light brought to focus by a lens are smeared out by a certain irreducible amount—even if all lens aberrations are perfectly corrected.

Instead of a sharp pinpoint, light is actually focused into a fuzzy bulls-eye pattern. Its bright center is named the Airy disk, after the British scientist who first described it.

[…]

The shocking thing few camera-buyers realize is that these fuzzy blobs are often larger than the individual pixels in a digital camera sensor.

Fancy professional cameras have giant pixels, relatively speaking, whereas a point-and-shoot has to shrink its pixels to smaller and smaller sizes as it keeps upping the megapixel value. There comes a point where the diffraction caused by the lens creates an Airy disk that’s much larger than the pixel. Post-processing by the camera can compensate for some problems with tiny pixels, but it can’t create detail that never existed within the camera in the first place.

Or something like that–you should read Ross’s much more technical and camera-savvy explanation. He demonstrates the problem with a typical outdoor photograph from a point-and-shoot camera.

His suggestion: stick with 6 or 7 MP cameras, because anything larger than that is just giving you “needlessly bloated file sizes.” His other suggestion: don’t buy your camera from a company that keeps lying to you about picture quality.

“Diffraction and Fraud in Digicams” [Petavoxel.wordpress.com]
“The Great Megapixel Swindle: An Example” [Petavoxel.wordpress.com]

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