Resolution

The term resolution is used to describe the quality or sharpness of images that are displayed on computer monitors or printed onto pages. Generally speaking, low-resolution images are of a lesser quality than high-resolution images. Resolution is expressed differently, depending on whether an image appears on-screen or in print.

The resolution of computer monitors is expressed in elements called pixels. Displayed as a set of red, green, and blue dots, pixels are the smallest pieces on a screen that can be manipulated. For example, the brightness or color of a pixel can be adjusted. Pixels normally are expressed in the form of two numbers (such as 640 x 480). When multiplied, these numbers reveal the total number of pixels a screen can display (such as 300,000). The value 640 corresponds to the number of pixels a screen can display across an individual horizontal line, of which there are a total of 480.

The earliest computer monitors were not capable of displaying the color images that are so important to Web pages and e-commerce. Instead, they were monochromatic and displayed text characters in green or orange. During the 1980s and early 1990s IBM developed display technologies like the Color Graphics Adapter (CGA), Enhanced Graphics Adapter (EGA), Video Graphics Array (VGA), and Extended Graphics Array (XGA) that allowed monitors to display greater numbers of colors and pixels. In the early 2000s, the Ultra Extended Graphics Array (UXGA) standard was supported by most computer monitors. In tandem with enough video memory and the right graphics card, UXGA made it possible to achieve resolutions of 1600 x 1200 pixels and display 16.6 million colors. Around the same time, flat-panel displays and rear-projection monitors were evolving, holding the potential to improve the quality of images users saw on-screen.

When the term resolution is used to describe the quality of a printed image, it is expressed in dots-per-inch (DPI), or the number of dots a printer can fit into one linear inch. A printer capable of printing 600 DPI can produce 360,000 dots in every square inch. The resolution of an image on-screen may not correspond with its resolution in printed form, since each depends on the equipment on which it is viewed or printed. However, the resolution of a printed or viewed image generally will improve if its size is reduced, or become poorer if its size is enlarged. This corresponds with the concentration of pixels or dots.