Digital Photography: The Missing Manual

Image Resolution and Memory Capacity

The first number you see in a digital camera description is its megapixel rating. A pixel (short for picture element) is one tiny colored dot, one of the thousands or millions that compose a single digital photograph. (One megapixel equals one million pixels.) You can’t escape learning this term, since pixels are everything in computer graphics. The number of megapixels your camera has determines the quality of your pictures’ resolution (the amount of detail that appears). A 5-megapixel camera, for example, has better resolution than a 3-megapixel one. It also costs more. How many of those pixels you actually need depends on how you’re going to display the images you shoot.

Resolution for Onscreen Viewing

Many digital photos never get further than a computer screen. After you transfer them to your computer, you can distribute the images by email, post them on a Web page, or use them as desktop pictures or screen savers.

If such activities are the extent of your digital photography ambition, you can get by with very few megapixels. Even a $100, 2-megapixel camera produces a 1600 x 1200-pixel image, which is already too big to fit on the typical 1024 x 768–pixel laptop screen (without zooming or scrolling).

Resolution for Printing

If you intend to print your photos, however, your megapixel needs are considerably greater. The typical computer screen is a fairly low-resolution device: most pack in somewhere between 72 and 96 pixels per inch. But ...