Each pixel in a computer image is perfectly square, arranged on a perfect grid, and colored uniformly — that is, each pixel is one color and one color only. Put these pixels together, and your brain perceives them to be an everyday, average photograph.

The display on your computer's monitor is also made up of pixels. As with image pixels, screen pixels are square and arranged on a grid. For instance, a typical monitor display measures at least 800 screen pixels wide by 600 screen pixels tall. These screen pixels are kind of tiny, so you may not be able to make them out. Each one generally measures around 1/72 inch across.

To understand the relationship between screen and image pixels, open an image. After the image comes up on-screen, double-click the Zoom tool in the Toolbox, or choose View, Actual Pixels. The Magnification box in the Status bar lists the zoom ratio as 100%, which means that you can see one pixel in your image for every pixel displayed by your monitor.

To view the image pixels more closely, enter a value of 200% in the Magnification box. A 200% zoom factor magnifies the image pixels to twice their previous size so that one image pixel measures two screen pixels tall and two screen pixels wide. If you change the zoom factor to 400%, Elements gives you a total of 16 screen pixels for every image pixel (4 screen pixels tall by 4 screen pixels wide).

Remember that the zoom factor has nothing to do with the size at which your image would print or display if e-mailed to a friend or posted on the Web — it affects only how your image looks on-screen at that moment. If you want to see on-screen an approximation of your image's print size, choose View, Print Size. Bear in mind, though, that this is only a very rough approximation.