Computer Monitor Features and Types: A Comprehensive Guide
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A monitor is the output device that displays the visual information generated by a computer, turning the data processed inside the machine into text, images, and video you can see on screen. 
The monitor connects to the computer's graphics card and continuously redraws the picture many times per second. While its job sounds simple, the technology behind a monitor, the way it forms each pixel, and the numbers on its spec sheet all affect how sharp, smooth, and comfortable the display feels. The sections below explain the main monitor types and the characteristics that matter when choosing one.
What are the main types of monitors?
Monitors fall into a few core technology families, each forming the on-screen image in a different way. The four you are most likely to encounter are CRT, LCD (in active and passive variants), and plasma displays.
CRT monitors are the original standard type, built around an electron beam tube (cathode-ray tube). A beam of electrons strikes the inside surface of the tube, which is coated with phosphor, and under that beam each point on the screen glows in one of three colors — red, green, or blue. CRTs are bulky and heavy because the tube needs physical depth behind the screen, and they have largely been replaced by flat-panel displays.
Liquid crystal (LCD) monitors form their image without glowing phosphor. Instead, a miniature liquid crystal element changes its optical characteristics under the action of an electrical current, controlling how much backlight passes through at each point. This design lets an LCD monitor be only a couple of centimeters thick, which is why flat panels displaced the deep CRT cabinet.
LCD monitors themselves split into two groups according to how the minimum elements of the screen image matrix are controlled — active matrix and passive matrix:
- Active matrix (TFT) — the higher-quality and more valuable option. A TFT monitor uses a dedicated color-control system in which each screen element (pixel) has its own thin-film transistor acting as a controller. As a result, the picture on a TFT monitor can change instantly without leaving "traces" or smearing on the screen.
- Passive matrix (DSTN) — has no per-pixel transistor system. The image looks paler and changes with a noticeable delay, which is why active-matrix panels became the standard.
Plasma monitors form the image with plasma: tiny cells of ionized gas that change color under the influence of an electric current. Plasma technology was used mainly in large displays and televisions, where it offered strong contrast and wide viewing angles.
How is the size of the screen "grain" measured?
The "grain" of a monitor is the size of its smallest visible point, the pixel, and it directly determines how fine or coarse the image looks. This value, also called dot pitch, is measured in tenths of a millimeter — the larger the grain, the coarser the picture appears. On 17-inch CRT monitors of different brands, the dot value typically falls in the range of 0.28 to 0.20 mm, with the smaller figure giving a crisper image.
What do monitor resolution and refresh rate mean?
Resolution and refresh rate are the two headline characteristics that describe how detailed and how smooth a monitor's image is. Resolution sets how many dots make up the picture, while refresh rate sets how often that picture is redrawn.
Resolution is the number of minimum image elements — "dots" — that fit on the monitor screen, expressed as two values: dots horizontally by dots vertically. The more dots, the less grainy and higher-quality the image. Common image modes have historically matched specific screen sizes:
- 640×480 — standard mode for 14-inch monitors;
- 800×600 — standard mode for 15-inch monitors;
- 1024×768 — standard mode for 17-inch monitors;
- 1152×864 — standard mode for 19-inch monitors;
- 1280×1024 — standard mode for 20-inch monitors;
- 1600×1200 — standard mode for 21-inch monitors;
- 2560×1800 — Retina display, such as on a 15-inch MacBook Pro.
In practice a monitor can often be set to a resolution higher than its standard mode, but pushing the setting too far can shrink text and detail to a point that strains your eyes, so the comfortable resolution matters as much as the maximum one.
Maximum scan rate, or refresh rate, can be thought of as the monitor's equivalent of a "frame refresh rate" — how many times per second the screen image is redrawn. The higher the refresh rate, the less the monitor screen appears to "blink" or flicker.
For comfortable work, the vertical refresh rate should generally be no lower than 85 Hz, meaning the image on the screen is renewed at least 85 times per second. A lower frequency produces visible flicker that is tiring and potentially harmful to your eyes, which is why refresh rate is an important spec to check alongside resolution.
The monitor is one of several core components covered on our PC section. If you are new to how these parts and programs fit together, our beginner's explainer on what software is is a useful companion read.
