How To Select the Best Display for your Home Theater Projection

Now that you know the 4 different technologies available, the question is ask is then which display technology should you get? Naturally, if cost isn't a consideration, you should be buying the best (and most expensive) projector you can get your hands on. Unfortunately this is never the case, at least not for the majority of us. So it then becomes important to know the pros and cons of each technology and what you are paying for.

CRT Projectors

Most of us would have had experience with CRT projectors from the projectors used in school. CRT projectors, being large and heavy, are generally fixed installations. Each of the three colours from the CRT "guns" combine to form the image on the screen. Colours are emitted using electrons and therefore do not have a fixed number of pixels. This means that CRT projectors are able to project clear images from sources with different resolutions. CRT projectors are unable to achieve the high quality images of modern projection technologies and are typically less bright. However, a properly calibrated CRT projector can still produce images decent enough to fool the untrained eye. Unfortunately, there is need for periodic calibration of CRT projectors, which can only be performed by a trained professional.

DLP Projectors

In DLP projectors, a colour wheel is placed between the lamp and the DLP chip to produce colours. The spinning colour wheel exhibits an anomaly known as the "rainbow effect". These rainbows are actually due to the after effects of the light source passing through the rapidly spinning colour wheel. The "rainbow effect" appears as flashes of red, green and blue after shadows such as when one looks on at a fast moving light source. To reduce this effect, the spinning rate of the wheel must be increase relative to the frame rate of the video. Video frame rates are typically 60 frames per second, or 3600 frames per minute. If the wheel spins at 4 times the video frame rate, it needs to rotate at 14,400 rounds per minute (rpm). However, there is a maximum rotational speed limit on wheels, usually in the range of 15,000 rpm. This means the video frame rates cannot increase too much or the rainbow effect will start becoming visible. Note that projector specifications describes wheel speed as 2x, 3x, 4x; 2x means 2 times video frame rate, and so on.

Other than this small defect (which is usually unnoticeable), DLP projectors are able to achieve the highest image quality to date among all projection technologies.  DLP images have perfect geometry and great contrast. They also do not suffer from phosphor burn-in (burn out of pixels due to prolong projection of a single tone at one spot, such as channel logo) as with LCD projectors. And because colours are produced using a colour wheel, DLP projectors do not suffer from the yellowing of images (after prolonged used) like that of LCD projectors.

However, DLP are reported to have longer response time compared to other projection technologies when upscaling images. Gamers opting use projectors should take this into consideration especially if they are concerned with games requiring quick reaction.

LCD Projectors

LCD projectors usually consist of three panels. Each of the panels act as a prism that allows one primary colour (blue, red, or green) through its pixels. These colours then forms the image like it does in a CRT projector. Because of the fixed number of panels on the projector, LCD projectors have a fixed number of pixels. The pixels are activated by electrical signals, which decide which pixel allows light to pass through.

LCD projectors are known to produce greater colour definition than DLP projectors due to the rainbow effect found in DLP projectors. However, the technology of LCD requires the pixels to be primed before being used, and pixels that are primed appear as grey with back light. This is evident when you switch off your LCD screen. For a short moment before the screen goes black, it appears pseudo grey. That is the "colour" of primed LCD pixels. Therefore LCD pixels are unable to show true black, consequently, contrast ratios in LCD projectors are poorer than other types. New LCD projectors with high contrast ratios have ratios as high as 800:1. in comparison, DLP projectors contrast ratios can be as high as 3000:1.  

Home theatre projector technology has come a long way since the time of CRT. While CRT projectors continue to be available in the market, the future of home theatre is definitely HD. If you're just starting to looking for a home theatre projector, either a LCD or DLP is the choice to make.