Rear-projection TVs: CRT, DLP, LCD, and LCoS
(updated August 4, 2005)
Thinking of going big? Sure, you could buy an 80-inch plasma, but most people who want to maintain a good credit rating will opt for a rear-projection television (RPTV) instead. These sets start at about 42 inches diagonal, and the majority support the wide-screen, 16:9 aspect ratio and have built-in HDTV tuners. Their big screens hide two basic varieties of display technology: old-fashioned CRT tubes; and microdisplays that use DLP, LCD, or LCoS technology. Here's an introduction to the choices.
Upside: Relatively inexpensive; excellent black-level performance; still the best picture quality in a proper environment with proper setup.
Downside: Deep cabinets; need periodic maintenance; not ideal for bright rooms; narrow viewing angle; softer image than microdisplays; most cannot display computer signals
Forecast: These dinosaurs are quickly being phased out in favor of lighter, lamp-driven microdisplays, and their demise in clearly in sight.
Mitsubishi, producer of the WS-55315, still sells a full line of CRT-based RPTVs, but the popularity of these large sets is fading fast.
Relatively low prices will keep CRT-based big screens in the game for another couple of years, and videophiles may indeed point out that they still provide superior image quality in many ways. They still have better black levels than any microdisplay; they generally have deep, well-saturated color; and they can achieve a sharp picture if adjusted properly. The image quality issues noted earlier, however, and especially their significant bulk, make these beasts destined to die off sooner rather than later.
Smaller box: Microdisplays are lighter, shorter, and thinner than CRT-based rear-projection HDTVs.
Upside: Good black-level performance; no maintenance required to preserve sharpness; often computer-capable; thin and light compared to CRT.
Downside: Expensive; some rainbow effects; video noise in dark areas; periodic lamp replacement required.
Principal brands: Samsung, Toshiba, Mitsubishi, Panasonic, LG, RCA
Forecast: DLP is only getting cheaper and more popular, although LCD will give it plenty of competition.
Samsung's pedestal-mounted HL-P5085W DLP TV shows off the possibilities of microdisplay design.
One potential problem with DLP sets is known as the rainbow effect. Some people can see brief streaks of color on these TVs, especially when moving their eyes across the screen. This is caused by the fact that the single DLP chip uses a color wheel to create red, green, and blue, and hence all colors. The occurrence of these rainbows has been significantly reduced with the advent of newer, faster color wheels, and most people who watch a DLP never see rainbows at all (and the few who do usually see them only occasionally). DLP HDTVs do introduce a bit more low-level video noise, which can look like tiny dancing pixels or motes in shadowy areas, than other microdisplay TVs.
Upside: No rainbow effect; no maintenance required to preserve sharpness; often computer-capable; thin and light compared to CRT.
Downside: Expensive; blacks not quite as deep as DLP; periodic lamp replacement required.
Principal brands: Sony, Hitachi, Panasonic, LG
Forecast: LCD has made some tremendous leaps in performance and will continue to challenge DLP as prices fall fast.
The striking Hitachi 50VS810 LCD looks like a plasma from the front.
Another area where DLP has an image-quality advantage is something called the screen-door effect. If you sit close to an LCD, you may notice a faint grid of pixels, much like a screen door, overlaid atop the image. You're seeing the space between the pixels, which is more visible on LCD than on the other two microdisplay technologies. It's generally not noticeable even on LCDs unless you sit closer than twice the diagonal measurement of the screen.
LCD's big advantage over DLP, and one that it shares with LCoS, is lack of the rainbow effect--a big deal if you see rainbows on DLP sets, and a moot point if you don't. Don't put too much stock in the slightly higher native resolution afforded by some LCD chips; in the big scheme of things, 1,386x788 doesn't provide much of a sharpness boost over 1,280x720. DLP makers have also claimed that the organic compounds in LCD chips degrade over time, while DLP chips do not. While this is essentially true, it has little impact on real-world product life span because LCD chips still last very long time under normal working conditions. While LCoS and DLP makers tout the "inorganic" nature of their chips, we don't consider that a major reason to choose one technology over another.
Upside: Excellent interpixel fill; no maintenance required to preserve sharpness; thin and light compared to CRT; more dependent on variants (below).
Downside: Periodic lamp replacement required; more dependent on variants (see below).
Principal brands: JVC, Sony, Hitachi
Forecast: LCoS is back from the dead, and two radically different variants prove the technology has plenty of staying power.
JVC's HD-52Z575 is the company's first attempt at an LCoS-based microdisplay RPTV.
JVC (HD-ILA): JVC has been producing LCoS-based front projectors for years under the D-ILA (Direct-drive Image Light Amplifier) brand, and in 2004 the company proffered a line of rear-projection sets, exemplified by the HD-52Z575 (pictured) and employing yet another abbreviation: HD-ILA. They're priced very competitively with DLP and LCD sets and offer the same resolution (1,280x720) as well as the brightest picture and best interpixel fill we've seen on a projection TV. Unfortunately, black level wasn't as good as either LCD or DLP, and we ran into some other issues (see the review for more). JVC has announced 1080p HD-ILA televisions that will appear later in 2005.
Sony (SXRD): Unlike JVC, Sony decided to charge an arm and a leg for its LCoS variant, dubbed SXRD (Silicon X-tal Reflective Display or Silicon Crystal Reflective Display). Initially available only in the Qualia 004 front projector ($27,000) and Qualia 006 70-inch rear-projector ($13,000), the 1,920x1,080 SXRD chip looks to be an excellent candidate for the best microdisplay technology yet. Initial reports indicate that it delivers excellent black levels, a minimum of video noise, and numerous other refinements. We expect the company will officially announce lower-priced SXRD-based HDTVs by January 2006.
Hitachi: The third big-name player hasn't cooked up a fancy name for its LCoS-based lineup, and in terms of pricing, Hitachi's sets fall somewhere between those of JVC and Sony. Since these models won't be released until late 2005, we don't know much about them yet, but stay tuned.