August 2002|LCD monitors are some of the neatest things to come out of the ongoing technology revolution. This isn't to say that there's no room in today's digital studios for the old CRT monitors that we all grew up with and that most of us still use. Au contraire; I like CRT monitors, especially for video applications. I've reviewed several HDTV sets and video monitors and I found that for video-realistic image quality, a good CRT is very hard to beat. Your living room TV generally looks great and would work fine as a computer monitor if it had been designed for resolution instead of being optimized for brightness and large-area contrast. This is the reverse of the CRT studio monitors, which have less brightness than a TV set, but are quite capable of maintaining a tighter, high-resolution pixel spacing across the screen without any distortion.
But suppose you are putting together the "ultimate" DVD or HD production studio—which is best for you? LCD or CRT? Are there even any LCD or CRT monitors that can support the full 1920x1200 high-definition image? Sure, but we're getting ahead of ourselves. Let's first review the basics.
CRT monitors direct their electron beams at the phosphor faceplates, through special aperture masks or grills like Sony's Trinitron that work to maintain color separation and pixel resolution. CRTs used for video applications also use aperture masks or grills, but those grills are sometimes lower resolution than computer applications and usually not capable of withstanding the electron beam current caused by a full-screen, maximum-contrast white background image—like a Mac or Windows desktop. Large-beam currents heat up the aperture masks and cause distortions across the image. CRT monitors have to overcome these problems to achieve higher resolutions by building stronger, thicker aperture masks and by using less electron beam current, which means dimmer images. The problem of maintaining a crisp, clear high-resolution image is difficult enough in the center of the CRT's screen, but this problem is even worse in the in the hard-to-reach screen corners—especially with shorter, more compact monitors.
LCD monitors have none of the CRT monitors' problems—not to the same extent, anyway. An LCD monitor is built by taking a large LCD screen and mounting a good-sized, multi-tube fluorescent lamp set behind it. Unlike CRT monitors, a LCD monitor does not lose resolution with contrast and brightness—as long as the LCD does not overheat, which won't happen with the small lamps used in monitors. An LCD monitor's resolution is set at the factory when the LCD's pixels are formed on the glass—and that resolution never changes as long as the glass itself remains intact.
So what if you want to display images of different resolutions on an LCD monitor with a fixed pixel array? We know what happens with a multi-synced CRT—the little electron beam just dances around the aperture mask with a different beat and forms a decent image regardless of whether it's of video resolution or SXGA or even HD graphics. LCD monitors (like LCD projectors) use the new technology of "resizing," which means that the desired digital image is mathematically "recalculated" to fit into the available pixels—and we all know that means that the LCD's image will look the best with "native" resolution images and a little off with most other images. If you want to display 1920x1200 pixel resolution HD images, you better get an LCD with at least that many RGB pixels.
Playing the Angles
So what's the bottom line? LCD monitors can provide better "graphical" images in their native resolution—especially with more evenly crisp detail even in the hard to reach corners—than a similarly-sized CRT monitor. We can argue about brightness and "large-area" contrast ratio (not to be confused with the on-off pixel contrast ratio) between LCDs and CRTs because for any winning LCD, I can usually find a winning CRT. And speaking about winning CRTs—try video images. CRTs win the video contest because they are more "analog" and they usually offer better, more photo-realistic gray scales and better color saturation along with a much faster response time.
Response time? What's that got to do with anything? If you really want to know, just take one of the so-called "wide viewing-angle" LCDs and attach a fast-moving video signal to it. When the little LCD molecules can't move fast enough to keep up with the on-screen action, the image begins to look out of focus. The slower the response time, the more out of focus it looks while the on-screen image is moving. Once the image stops moving, everything jumps back into an amazingly sharp focus. LCDs generally have response times that are measured in tens of milliseconds whereas a CRT's dancing electron beam moves in microsecond bursts. Plus, LCDs with wide viewing angles have molecules that move even slower. And that illustrates another difference between CRTs and LCD monitors: viewing angle.
In the old days, an LCD monitor or laptop LCD display only looked good from one, rather limited, direction. The image on a CRT screen can be seen, generally without distortion, from just about any direction—even when looking at the side of the display. Try that with a typical, cheap LCD monitor and you'll see something in reverse color if you see anything at all. To overcome this viewing angle "problem," LCD manufacturers made several improvements to the way that the LCD molecules are arranged in between the LCD's little glass sandwich so that they "appeared" the same under wider viewing angles. These improvements tend to slow down the response time, however, and anything more than a few milliseconds is noticeable. Why? Because the entire video frame is usually updated once every 16.667ms, in sync to a 60 cycles per seconds rate. Anytime an LCD's pixel can't respond (switch between on and off) within 16 milliseconds or so, it's going to be late to dinner, so to speak. That makes it look out of focus.