Resolution
As with any camera, picture quality is key. With digital cameras, photo quality is measured in terms of "resolution." The higher the resolution, the sharper the images. Most cameras offer a number of adjustable resolution "settings" (low, medium and high). But the key is a camera's "maximum resolution" rating. Basic models have a maximum photo resolution of about 640 x 480 pixels. Higher-quality "megapixel" models have maximum resolutions of 1'280 x 960 or more for truly photographic-quality prints.

A megapixel is one million pixels. Pixels are the smallest measure of a digital photo's clarity (or resolution). The greater the number of pixels, the greater the clarity of a photo. High-end digital cameras are capable of producing digital photos with megapixel resolution.

Beware of claims about resolution for cameras because there are two kinds of resolution: optical and interpolated. The optical resolution of a camera is an absolute number because an image sensor's pixels or photoelements are physical devices that can be counted. To improve resolution in certain limited respects, the optical resolution can be increased using software. This process, called interpolated resolution, adds pixels to the image to increase the total number of pixels. To do so, software evaluates those pixels surrounding each new pixel to determine what its color should be. For example, if all of the pixels around a newly inserted pixel are red, the new pixel will be made red. What's important to keep in mind is that interpolated resolution doesn't add any new information to the image-it just adds pixels and makes the file larger. This same thing can be done in a photo-editing program such as Photoshop by resizing the image. Beware of companies that promote or emphasize their device's interpolated (or enhanced) resolution. You're getting less than you think you are. Always check for the device's optical resolution.

Color depth
Resolution isn't the only factor governing the quality of your images. Equally important is color. When you view a natural scene, or a well done photographic color print, you are able to distinguish millions of colors. Digital images can approximate this color realism, but whether they do so on your system depends on its capabilities and its settings. The number of colors in an image is referred to its color depth, pixel-depth, or bit depth. Older PCs are stuck with displays that show only 16 or 256 colors. However, almost all newer systems can display what's called 24-bit True Color. It's called True Color because these systems display 16 million colors, about the number the human eye can distinguish.

How many pixels do I need?
(Recommendations based on researches of the New York Institute of Photography)

Your best bet is to choose a camera with a resolution appropriate for your needs. If you're primarily planning to view your digital camera's images on a computer monitor (e-mail attachments, Web pages, online auctions) or on a TV screen (using video-out to give a slide show), then high resolution isn't very important. For years, Web designers have used 72 dots per inch (dpi) as a good approximation of the maximum resolution a screen will display. You can display your images at higher resolution--they'll just take longer to load and won't look any nicer. Using this "Rule of 72," even an entry-level 640 x 480 camera will produce good-looking images at sizes up to approximately 7 by 9 inches.

Maximum DISPLAYED image sizes (using Rule of 72):

Printed images are a different story. If you're printing on a home printer or using an online service to get prints from your digital camera, plan on having at least 150 dpi ("Rule of 150").

Maximum PRINTED image sizes (using Rule of 150):