Screen size

main: Screen size

Diagonal size

The size of a display is typically given as the distance between two opposite screen corners. One problem with this method is that it does not distinguish between the aspect ratios of monitors with identical diagonal sizes, in spite of the fact that a shape of a given diagonal span's area decreases as it becomes less square. For example, a 4:3 21" monitor has an area of ~211 square inches, while a 16:9 21" widescreen has an area of only ~188 square inches.

This method of size measurement dates from the early days of CRT television when round picture tubes were in common use, which only had one dimension that described display size. When round tubes were used to display rectangular images, the diagonal measurement of these was equivalent to the round tube's diameter, hence this was used.

Another historically problematic practice is the direct measurement of a monitor's imaging element as its quoted size in publicity and advertising materials. Especially on CRT displays, a substantial portion of the imaging element is concealed behind the case's bezel or shroud in order to hide areas outside the monitor's safe area due to overscan. Seen as deceptive, widespread consumer objection and lawsuits eventually forced most manufacturers to instead measure viewable size.

Imaging technologies

• Liquid crystal display (LCD). TFT LCDs are the most popular display device for new computers.
• Passive LCD produce poor contrast, slow response, and other image defects. These were used in most laptops until the mid 1990s.
• Thin Film Transistor LCDs give much better picture quality in several respects. Nearly all modern LCD monitors are TFT.
• Cathode ray tube (CRT)
• Raster scan computer monitors, which produce images using pixels. These were the most popular display device for older computers.
• Vector displays, as used on the Vectrex, many scientific and radar applications, and several early arcade machines (notably Asteroids) - always implemented using CRT displays due to requirement for a deflection system, though can be emulated on any raster-based display.
• Television sets were used by most early personal and home computers, connecting composite video to the television set using a modulator. Resolution and image quality were strongly limited by the display capabilities of television.
• Plasma display
• Video projectors use CRT, LCD, DLP, LCoS or many other technologies to send light through the air to a projection screen. Front projectors use screens as reflectors to send light back, while rear projectors use screens as diffusers to refract light forward. Rear projectors are often integrated into the same case as their screen.
• Surface-conduction electron-emitter display (SED)
• Organic light-emitting diode (OLED) display
• Penetron military aircraft displays