A Short Course Book Sensors, Pixels and Image Sizes  Pixels and
Screen Display  At 800 x 600 (top), Photoshop and the image
being edited fills the screen. When the screen resolution is
increased to 1024 x 786 (middle), the image is smaller and at
1280 x 1024 (bottom) even smaller. When a digital image is
displayed on the computer screen, its size is determined by
three factors—the screen's resolution setting, the screen's
size, and the number of pixels in the image.  The Screen's
Resolution  The size of each pixel on the screen is determined
by the screen's resolution setting. The resolution is almost
always given as a pair of numbers that indicate the screen
setting's width and height in pixels. For example, a monitor may
be specified as being a low-resolution 640 x 480, a medium
resolution of 800 x 600, or a high-resolution of 1024 x 768 or
more. (The first number in the pair is the number of pixels
across the screen. The second number is the number of rows of
pixels down the screen).  This is a 1680 x 1050