Image quality is generally considered to be better on an LCD, as each pixel is generated by a specific set of transistors in the screen, which produces a crisp image. However, some features that fall under the general heading of image quality might not favor an LCD, including viewing angle, brightness, and contrast.
Early LCD monitors had a fairly narrow viewing angle that made clearly seeing the screen from anywhere but directly in front of it difficult. This has vastly improved, but LCDs still can't rival the viewing angle of CRTs which provide the same picture quality regardless of the angle. A monitor with a maximum vertical viewing angle of 120 degrees should not be hard to find at this point, with many monitors now being able to provide an even greater angle.
Brightness is an area that LCD monitors have the edge over CRTs, but it varies widely from unit to unit. The standard measure for brightness is referred to as “nits”, which have units of cd/m2 (candelas per square meter), where a higher number is better. Most LCDs currently available will provide a brightness specification of approximately 250 cd/m2 or better. As a comparison, the typical CRT monitor provides half the brightness of an LCD, as confirmed at Viewsonic's Monitor University.
Contrast is similar to brightness in the fact that it varies widely from unit to unit. All LCD screens get their brightness from backlighting behind the actual LCD films. This light has the tendency to wash out the colors and provide a close approximation on most colors. The contrast ratio of a LCD flat panel is the rating of how distinguishable various shades of color are. The higher the contrast ratio of the screen, the better the color representation is by the monitor. Contrast ratios are one aspect of image quality where CRTs still have a slight advantage; but, you will find that LCDs with a contrast ratio of 400:1 or better, will give you an excellent image.
Energy Consumption
LCD monitors definitely hold the edge over CRT monitors when it comes to being energy efficient. The huge tube in a CRT monitor is the source of most of its energy consumption, and a comparably sized LCD may use just a fraction of the electricity. Taking a look at an average 19” LCD monitor shows that it consumes 48 Watts during normal operation, which is less than your typical light bulb. In contrast, a 19” CRT such as this one from Viewsonic may draw up to 160 Watts. This could translate to noticeable savings on your electric bill.
Health and Comfort
The main benefit that LCDs have when is the reduced strain on your eyes. The reduced glare on the screen's surface, and the elimination of a typical CRT's “refresh”, can prevent your eyes from getting tired from extended use. A CRT monitor redraws the image on the entire screen as it refreshes, whereas an LCD monitor only changes the necessary pixels during a refresh.
There may also be the unquantifiable effect of reduced electromagnetic emissions on LCD monitors. The exact impact of electromagnetic emissions may not be fully understood, but in general less is considered to better. And, your back will appreciate an LCD when it comes time to move, as the example above shows a 19” LCD monitor weighs about ¼ as much as its CRT counterpart.
Response Times
LCD monitor response times have greatly improved over the past few years, and many LCDs are now fast enough to consider for serious 3D gaming. A few years ago a typical response time on an LCD may have been anywhere from 30 to 50 milliseconds, and today these numbers can get down into the single digits, with anything 25 milliseconds or less being quite common (lower is definitely better). Typical response times of 16ms to 25ms are what can be expected in most LCDs available today.
Final Words
In addition to some of the positives mentioned, many LCD monitors now incorporate other features to make them more practical and even fun. LCD monitors can now be found with integrated USB hubs, stereo speakers, and TV tuners, and for the right price HDTV is even an option.
LCD monitors will continue to replace CRTs as they become less expensive and the many benefits are realized by consumers.
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