Megapixels and Image Size

Each square on a monitor or phone display is a pixel. A megapixel is a million pixels, or 1000x1000 pixels. Webcams are generally either a low-quality .3 megapixels (close to the size of old standard-definition television broadcasts) or 1.3 megapixels, the size of an SXGA (1280x1024) monitor. Neither of those is large enough to yield satisfying print results, because of yet another dimension, pixels per inch (ppi) (also called dots per inch, or dpi).

When you display images on a monitor, 72 dpi looks fine. However, if you print that same image, it will look horrible at that resolution. You'll be able to see every pixel. If you're printing, you want an image somewhere around the 250 to 300 dpi range for good print results; most professionals use 300 dpi as the standard. That means, to get a quality 8x10-inch photo, you need a camera with at least 5 megapixels for a 250 dpi print and 7.2 megapixels for a 300 dpi print.

The first commercial Android phone, the T-Mobile G1, has a 3.2-megapixel camera. That's enough resolution to print a 300 dpi 5x7-inch photo, but no larger. There's no flash on the camera, so it doesn't handle low light well. The Nexus One and Motorola DROID cameras both ship with 5-megapixel cameras with flash. The Sony Ericsson Xperia X10 has an 8-megapixel camera, as does the HTC EVO. In fact, the EVO has an 8-megapixel camera on the back and a 1.3-megapixel camera on the front for video conferencing. Every phone I've tried has had a second or two lag in response when you press the button to snap a photo, but that's likely to improve as hardware improves.

Video resolution is lower than print resolution. High-definition (HD) video is at maximum just slightly bigger than 2 megapixels. However, video struggles against the amount of space it takes up, so most phones do not support HD video at this time.

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