An Introduction to Projection Technology

Projection television takes home cinema to its ultimate limits. No longer is the viewing experience restricted by the physical constraints imposed by a TV tube. With a front projector system an entire wall of your lounge becomes your TV screen. Movies appear as they would in the auditorium of a cinema. You view in total darkness for the best effect. Although there are some models which incorporate a tuner and audio amplifier, this is rare. To casually watch TV you must use the tuner in your VCR for video and your AV amplifier for sound.

Video projectors fall into two categories. Tubed and LCP (liquid crystal projection). Both have unique advantages that affect installation and performance. The tubed projector is a box sporting three lenses. They focus separate red, green and blue images on to the screen to build a TV image as large as you like. It is this type of projector that is commonly used in cinemas and at public displays. On these models, there's more to the optics than meets the eye. As each lens is on a different axis, the pictures don't naturally overlap. An electronic means for converging the picture is therefore provided and a pattern generator produces a grid which has to be focused and aligned so the squares are geometrically true. The process is repeated for all three tubes. If you're inexperienced it can take many hours and if you move the projector you must start again from scratch.

Consequently, tubed projectors are fixed assets usually installed by experts then rarely touched. As the lenses are wide angle, they provide big pictures close to the screen - typically a 60in picture at 2.5m. Typical mountings include ceiling fixing or even floor mounting in the middle of the room.

Your other projection option is more user-friendly. An LCP can be moved from room to room and requires no more set-up than a slide projector. At the heart of the LCP are a number (usually three) of liquid crystal panels. All are illuminated by a single high-wattage metal halide lamp. A complex series of dichroic reflectors and filters split the spectrally pure white light into rays of red, green and blue. Each of these beams illuminates a liquid crystal panel. The images from the panels converge at the focal point of a single lens. Focus and zoom are provided and on many models are controlled via an IR handset.

The disadvantage of LCP has been the so-called 'chicken-wire' effect. Superimposed upon the image is a criss-cross network of pixels or image elements. It is these individual cells that form the picture and, when magnified by the lens, they can become rather obvious.

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Hitachi CP-RS55 LCD projector

CNET editors' review
Reviewed by: Rich Malloy
Edited by: Felisa YangReviewed on 4/5/05
Release date: 12/1/04

Hitachi positions its Performa CP-RS55 as a dual-use projector, best applied to business situations but quite handy in the living room, as well. We might go a step further: in view of its compact size (11.2 by 8.0 by 3.2 inches)--not much larger than a cigar box--this 4.8-pound model is also well suited for mobile applications. Add to that a record-low price tag that occasionally dips below $800, and we might just call the CP-RS55 a basic, one-size-fits-all business projector.

Inside the stylish but understated silver-gray case is an LCD imaging engine, part of the reason for the projector's low price. Hitachi has upgraded this venerable technology with what it calls Progressive Scan Technology, which promises reduced flicker. Nevertheless, CNET Labs' tests revealed the typical trademarks of LCD technology: superior color handling (particularly with blues, in this case), a significant screen-door-like grid effect on projected images, and a lower-than-average contrast ratio (only 192:1).

Another traditional LCD drawback inherited by the Hitachi is the need for regular cleaning of the cooling fan's air filter. In other words, this model is better for tabletop use than for ceiling installations with limited access.
The CP-RS55 comes with a decent but spartan set of connectors and cables. The standard connectors (VGA, S-Video, composite video, and audio) are all present and accounted for, though the projector ships with only one VGA cable and an AC cable. The only surprise is an RS-232 port labeled Control, which, with an optional cable, enables you to control the projector either locally or via a network.

As you might have guessed by now, the old adage still stands: you get what you pay for, or in this case, you don't get what you don't pay for. The CP-RS55 lacks many of the features you would normally expect with projectors, such as a carrying case, a laser pointer, or optical zoom. The top panel of the projector has only three buttons, one of which toggles in four directions for menu navigation. This button deficiency is compensated for by the oversize remote control, which bristles with no fewer than 24 buttons. But unlike the remotes that come with the BenQ PB6110 or the InFocus X2 budget projectors, not one of these many buttons can page through a PowerPoint presentation, which is an egregious oversight for a business projector, budget or otherwise. Instead, they are dedicated to dubious features such as digital zooming and image freezing. You'll have to rely on your laptop or a mouse to page through presentations.

Despite cost-cutting, the Hitachi did well in our Labs tests, falling only a little short of its impressive advertised brightness of 1,500 ANSI lumens. In fact, even in its low-power, lamp-friendly Whisper mode, the CP-RS55 was able to outshine the Toshiba TDP-S20U. We also appreciated the CP-RS55's surprisingly short warm-up and cool-down times of only 22 seconds and 1 minute, 16 seconds, respectively. This model also runs quite cool; we noticed some warm areas near its fan exhaust, but nothing that was uncomfortably hot. In our tests, the greens produced by this projector seemed a bit yellowish, but our colorimeter showed that it handles reds and blues remarkably well. Contrary to what Hitachi claims, we did see a small amount of flicker, but nothing beyond the ordinary.

The Hitachi Performa CP-RS55's replacement lamp is rated for 2,000 hours of use, half that of other projectors. Hitachi charges $199 for the lamp, which works out to about 10 cents per hour--not exactly cheap, but better than average. Changing the lamp is fairly simple: you only need to remove three screws. Hitachi bundles the projector with a two-year warranty, but the lamp is covered for only 90 days or a surprisingly short 180 hours of use. The company's Web site lists only limited support services, such as replacement parts and accessories for the projector, but it does not indicate how to purchase them or what they cost. To get more information, you must fill out an electronic form or send an e-mail message to one of the tech-support mailboxes listed there. Toll-free phone technical support is provided seven days a week, from 8 a.m. to 8:30 p.m. CT.