There are two major types of computer monitors: CRTs, which are based on the same 100-year-old cathode-ray-tube technology as the first television, and LCDs, which are based on newer, liquid-crystal technology. Although CRT monitors are still optimum for some tasks, LCDs look slicker, take up less desk space, and can offer sharper image quality, and as a result, they have begun to dominate the market. Most CRTs offer only an analog connection, but more and more LCDs offer both digital and analog inputs. Which one should you use?
Let's take a step back. A CRT, or cathode-ray tube, monitor is an inherently analog device, while computers are purely digital devices. How does a twentieth-century analog appliance talk to a twenty-first-century digital machine?
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Analog (VGA) input |
They do so via a graphics card (also called a video card). Most computers have at least one analog input, which is sometimes labeled VGA (for video graphics array) or D-SUB, on the back of the computer.
The graphics card converts the computer's digital signal to an analog one, which it conducts to the monitor via an analog cable. Without getting into too much detail, the CRT monitor takes the analog signal and uses electron guns to manipulate phosphors and, well, it turns the signal into an image (read more about how CRT monitors work here).
A video card converts a computer's digital signal to an analog one, which a CRT translates into an image. |
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However, just as when you convert American dollars to euros or put written Japanese into English, something is always lost in translation. Because of the conversion from digital to analog, in general, CRT monitors deliver less accurate image quality than LCDs.
An LCD (liquid-crystal display), on the other hand, like a computer, is a digital device. Manufacturers are increasingly putting both an analog and a digital connection on LCDs. When connected via an analog connection, an LCD is vulnerable to the same distortions that affect CRT monitors. However, when connected via a digital connection, often labeled DVI (for Digital Visual Interface), no digital-to-analog conversion is required, and there should be no loss or corruption of the signal. As a result, when running at its native resolution, an LCD should give you a cleaner and crisper image than you'd see on a CRT.
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Digital (DVI) input |
CRTs rarely provide support for digital signals; DVI support is found primarily on LCDs. However, the advantage of digital signals for LCDs is of somewhat less importance now than it was a few years ago. Analog signal processing has improved to the point where major differences in image quality can be difficult to detect. Unless you're a pro photographer, a prepress professional, or someone else who needs superprecise, top-notch image quality, you should be fine using a CRT or an LCD on an analog signal.
If your LCD has a digital connection, you'll need a graphics card that has a DVI-I or DVI-D connector to take advantage of it. You'll also need a DVI cable (many LCD monitors come with only an analog cable). DVI-D refers to a digital-only connection, and DVI-I means that the connector can carry either digital or analog signals. Read the CNET editor's take | |
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