Lenovo PC 300GL Understanding Your Personal Computer 6267, 6277, 6287 - Page 20

Chapter 3. Video This section describes the video features of your computer, including monitors, the graphics controller, video modes, and other video features. Monitors Although there are various types of monitors, the most common distinguishing characteristics are resolution, dot pitch, scanning rates, screen size, and color. Resolution and Dot Pitch The entire image on a monitor screen is made up of many tiny dots. These dots are called picture elements or pels. The monitor resolution is described by the number of pels that fill the screen in an array of horizontal rows and vertical columns. For example, the pels might be arranged in a horizontal-by-vertical array of 640 x 480 pels to make up a typical screen image. Higher resolutions, such as 800 x 600 or 1024 x 768 pels, mean more dots on the screen. The benefit of higher resolutions is either displaying more information at one time or displaying the same information with a sharper image. Dot pitch refers to the space between the individual dots or pels. The inside of the monitor screen is coated with light-emitting materials called phosphors. Color monitors use three phosphors: red, green, and blue. The phosphor coating consists of dots arranged in a red-green-blue pattern. The distance from the center of one phosphor dot to the center of the next phosphor dot of the same color is the dot pitch. Dot pitch is measured in millimeters, such as 0.28, 0.31, 0.39, and 0.41. In general, the monitor with the highest resolution and finest dot pitch produces the sharpest image. A monitor with a fine dot pitch, such as 0.28, produces sharper, better defined characters than a similar monitor that uses a coarser dot pitch, such as 0.41. Monitor characteristics can be very important. A computer used extensively for detailed graphics might need a monitor that shows more colors, at a higher resolution and finer dot pitch, than one used exclusively for word processing. For some applications, a black-and-white (monochrome) monitor might work as well or better than a color monitor. Scanning Characteristics The phosphors on the inside of the monitor screen hold their brightness and color for a very short time. Therefore, the image has to be scanned (redrawn) many times each second to refresh the phosphors. The vertical refresh rate is the speed at which the image on the screen is redrawn (or scanned). Refresh rates are specified in hertz (Hz). The image is redrawn from top to bottom (or vertically). By the time the bottom pel rows are drawn, the top rows are starting to fade. There are two ways of redrawing the image: interlaced scanning and noninterlaced scanning. The interlaced method draws every other 12 © Copyright IBM Corp. 1998