FAQ's about LCD & DLP Projectors

A self-contained unit that combines three LCD (Liquid Crystal Display) panels and a high intensity light source for a complete computer and/or video projection device. LCD projectors come in a wide variety of sizes and specifications, so it can be very helpful to have the experts and United Visual help you make the right choice for your application. The basic design of an LCD projector consists of a light source, a prism to split light into Red, Green and Blue which is then passed through the transluscent LCD panels, combined and focused via optics onto a projection screen. LCD offers huge advantages over older CRT based projectors in brightness, size and weight.

The requirements vary from vendor to vendor, but we can provide a general rule of thumb to cover nearly all cases. First of all, use the same care you would with any electronic equipment; avoid exposure to extreme temperatures and impacts. But beyond common sense care, you must develop a filter cleaning regimen to greatly extend the life of your LCD projector and those costly lamps. All LCD projectors have one or more sponge or cloth intake filters. As a general rule of thumb, these filters must be cleaned or replaced after every 100-300 hours of projector use. Sponge filters can usually be blown out with canned air or run under water and then allowed to dry before re-installing. Failure to follow this regular procedure will likely cost you hundreds of dollars in repairs when the projector is 3-4 years old. In many cases, the LCD panels themselves will be damaged by overheating and the projector will be beyond economical repair. In addition, LCD projectors used regularly should be professionally cleaned internally at least every 2 years. This will remove the pesky dust particles that show on, or tint the projected image and more importantly clean out the built up dust and dirt that prevents good airflow to cool the lamp and electronic components. Lack of proper maintenance will cause premature failure of the lamp power supply (ballast) as well as the LCD panels themselves. If you know anyone that has needed these repairs, you'll understand why you want to avoid them!

A self-contained projector alternative to LCD technology using Texas Instruments DLP™ technology. DLP (Digital Light Processing™) typcially uses a single self-contained digital display chip, actually called a Digital Micromirror Device (DMD). The device contains millions of microscopic tilting mirrors that are tilted to either reflect light, or not, depending on the video signal. This complex, but ingenious device, actually only produces images in black and white, but a high speed rotating color wheel is introduced into the light path to transform the image into color. In contrast to LCD, the light does not pass through the DMD device, it is reflected by all these tiny mirrors. DLP projectors offer the same advantages over CRT as does LCD projection, while allowing lower power lamps to provide brighter, higher contrast images, but also introduces a mechanical device, the color wheel motor.

NO! This is the little white lie that DLP vendors tend to use by misinterpreting the actual advantage DLP has over LCD. While it is true that most, if not all, DLP projectors do not have intake dust filters, that doesn't automatically mean they will stay pristinely clean forever. The true reason for removing the filters is to prevent typical human nature from allowing DLP projectors to clog up, overheat and fail, just like LCD projectors do when the filters aren't cleaned. You can't get away with removing the filter on an LCD projector because little speckles of dust will end up on the panels and eventually obliterate the projected image. With DLP, it is rare that dust can settle on the one tiny DMD chip, which has a color wheel rotating and high speed in close proximity, in effect acting like a fan to blow away the dust before it settles. So in this respect, it's true that part of the projector doesn't need regular cleaning; the DMD chip and the dust filter that doesn't exist. However, because there is nothing filtering the airflow through the projector, which is still needed to cool the extremely hot lamp and the electronics it is baking, the annual or semi-annual cleaning by a professional is even more important. The fan(s) in a DLP projector will collect dust and be weighted down sooner than on an LCD and that makes the fan run slower. The reduced cooling and dust that is sucked into the projector cause the lamp power supply (ballast) to require more regular cleaning or they will fail due to overheating even sooner than in an LCD projector. Bottom line: DLP projectors need annual or bi-annual cleaning just like LCD projectors.

An ANSI lumen is a measure of brightness put out by a projection device, as standardized by the American National Standards Institute. Note these are not comparable to "lumens" expressed in non-ANSI terms (and used to measure, for example, the output of overhead projectors).

This depends on your room lighting conditions and screen size. As a rough guide, a rating of 150 to 300 ANSI lumens (the brightness of three-tube CRT projectors) is adequate with a 60" diagonal screen with room lights off, but you should look for something in the 700 - 800 range for a 100" to 150" screen with lights dimmed, and at least 1200 ANSI lumens when you go to a 300" screen or want to project in bright lighting conditions. Your best bet, of course, is to ask your sales rep to demo the projector under conditions typical to what you’ll see.

Most LCD projectors use a metal halide source, which offers a very white light and a life of 750 - 4,000 hours or more. They typically do not burn out, but gradually grow dimmer, giving you plenty of warning that it’s time for a replacement. With this type of lamp, total lamp life is not a very useful measurement, as the lamp will continue to function long after they're so dim you won't want to use them. So manufacturers' offer a peak rating—and peak lamp life is the time the lamp will last at 80 - 90% of total brightness.

The resolution of your computer display measures the amount of detail that can be seen in an image, expressed as the number of distinct horizontal and vertical lines visible on a test pattern.

VGA in an acronym for Video Graphics Array. VGA, SVGA and XGA all measure the resolution of the video signal being output by a personal computer. VGA consists of 640 vertical lines x 480 horizontal lines, SVGA 800 lines x 600 lines, XGA 1024 x 768, SXGA 1280 x 1024, and UXGA 1600 x 1200.

A video or computer image is made up of rows of horizontal and vertical pixels. Its resolution is limited by the number of distinguishable rows, or lines, that the monitor or LCD device can form. "Horizontal resolution" or, more properly, "horizontal lines" is the number of distinct lines that you can count going across the image--but if you look at your monitor, these lines would actually go up and down, or vertically. "Vertical resolution" measures the number of distinguishable lines you can count from top to bottom in the image.
In computer projection, the number of lines is only limited by the signal coming out of the computer and the quality of the projection device. In television, the number of vertical lines of resolution is fixed: the American, or NTSC, standard is 525 vertical lines. The number of horizontal lines will vary with the quality of the monitor or projector used, but is still limited to less than 400 by NTSC standards. This limit is one of the barriers that is broken with the introduction of Digital Television.

S-VHS was introduced in response to the criticism of the poor video quality of standard VHS recordings. S-VHS is not just a buzzword, but an entirely different system of recording video signals on VHS size tapes. However, it has never become a widely accepted format for consumers so it is a subject of confusion.
S-VHS records luminance and chrominance (b&w picture and color information, also called Y and C) separately, rather than as a composite signal. By doing this, the deck is able to record and playback a wider bandwidth, or a much higher resolution signal than a normal VHS deck. The signal is also output via a special s-video connector that also keeps the Y and C signals separate. The result is a much clearer, higher definition picture than VHS can produce. The horizontal resolution of S-VHS is around 400 lines, compared to 240 lines of normal VHS in SP mode.
S-VHS is most often used commercially or by educational institutions where they can record video with an S-VHS camcorder at 400 lines and then edit it on S-VHS editing equipment. This allows editing to be done with a very good signal so that even after multiple copies are made during the process, the final result is still higher than the quality of broadcast television. If standard VHS was used, the end result would be noticeably poor, even to an untrained eye.
Unfortunately, S-VHS rarely finds its way into homes because you won't find movies to rent in S-VHS. Also, if you make your own recording on the required special S-VHS tapes, most standard VHS VCRs won't play them.

S-Video connectors are used for a variety of high resolution signals. It was originally developed for use with S-VHS recorders, but is now the standard for DVD players and is also used for converting computer signals to video via a scan converter. The connector has four connections (see diagram), compared with two for a standard video connector. This allows the luminance and chrominance (b&w picture and color, also called Y and C) information to be transmitted separately allowing for a much wider bandwidth and less crosstalk. The wider bandwidth translates to a horizontal resolution of about 400 lines compared with the normal 240 to 320 lines with conventional composite video connectors. Less crosstalk means there will be less "snow" or "color noise" in the picture. For reference, the S-Video connector's pin outs are as follows: Pin 1 - Y ground, Pin 2 - C ground, Pin 3 - Y signal in/out, Pin 4 - C signal in/out.

DTV, Digital Television, is a new broadcast standard that will provide vastly improved picture and sound quality when compared to the current NTSC broadcast standard in the United States. With DTV, viewers can see images up to six times the resolution of their current TV’s. HDTV, High Definition Television, is one of the possible formats that will be transmitted when DTV becomes available. HDTV broadcasts are at the top end of the DTV spectrum. These broadcasts will have the best sound quality, the ability to broadcast in a wide screen format using a 16:9 aspect ratio, and the best picture quality. For more details, see our Tech Tip, DTV:Seeing is believing provided courtesy of Sharp Electronics.

An aspect ratio refers to the dimensions of a television screen or other screen. The ratio refers to the width of the screen in relation to the height of the screen. The aspect ratio of today's traditional TV is 4:3. For comparison, the aspect ratio of a square screen would be expressed as 1:1 or 4:4. The aspect ratio of HDTV is 16:9. This is similar to the aspect ratio that many motion pictures are shot in. The 16 refers to the width of the screen and the 9 refers to the height of the screen.