Additional Considerations
When making a rear-projection television purchase, make sure you include the following factors: What you want to watch (and where), Brightness, Contrast Ratio, Pixel Density, Color Reproduction, Inputs, Viewing Angle, and Price.
Brightness: Without sufficient brightness your image will look muddy and soft, even in a dark room. Check the ANSI Lumens rating. Relatively speaking, projection assemblies producing 1,000 ANSI Lumens is plenty for a rear-projection television. However, since the light is reflected onto a screen, the light intensity emanating from the screen, into the viewing room itself, is more important.
The measure of brightness that comes from the screen surface in any particular direction is calculated in cd/m2 (Candela/Square Meters), also called 'nits'. Brightness measurements on rear-projection televisions can vary widely, anywhere from 400 to 800 cd/m2. This specification should be labeled in the specifications sheet for the television; it may also be listed as Foot Lamberts(fL), where 1 fL is approximately 3 cd/m2.
In the final analysis, don't get bogged down in the math; regardless of what the numbers say, make sure you are comfortable with the brightness of the image that is on the screen.
Contrast Ratio: Contrast ratio complements brightness. High contrast ratios deliver whiter whites and blacker blacks. A rear-projection television may have a great Lumens and Foot Lamberts rating, but if the contrast ratio is low, your image will look washed out. A Contrast ratio of at least 1,000:1 or higher is considered excellent.
Pixel Density: Pixel Density is important, with regard for LCD/DLP units. As stated earlier, LCD and DLP-based video projectors have a fixed number of pixels on their display chips. If most of your viewing is HDTV, get as high a native pixel count as possible. For instance, 720p HDTV signals require a 1280x720 pixel count to give you a one-for-one representation of a 720p signal while, as mentioned earlier, a 1080i HDTV input signal needs a native pixel count of 1920x1080 for a one-for-one representation of the 1080i signal. If a projection set's pixel count is less and it accepts HDTV input signals, the signal is scaled to fit the number of pixels on the chip.
On the other hand, a native pixel count of 1024x768 is sufficient for DVD. In addition, some projection sets also upscale a lower resolution image to match a higher pixel count on the chip. Scaling can work both ways. Check specifications for this capability.
Color Reproduction: Check for natural flesh tones and color depth. Check how colors look in the brightest and darkest areas of the image. Check the degree of color stability from input to input. Everyone has a slight difference in color perception and what looks pleasing. Look carefully.
Viewing Angle: All projection televisions have a problem with side viewing. Although viewing angles for rear projection televisions have improved greatly in recent years, with some offering 130 degrees or more, optimum viewing is still best from the center of the screen out to a 45 degree angle, with acceptable viewing possibly out to 90 degrees. In other words, all the viewers sitting on a large couch shouldn't have a problem, but someone sitting in a chair off to the side will not get an optimum view of the screen.
Inputs: Make sure the projector has the inputs you need, such composite and S-video for analog sources, component inputs for DVD, and DVI or HDMI inputs for HDTV. Some rear-projection televisions now have VGA or similar inputs that enable it to be used with a computer for video presentations or game play.
Price: Rear-projection televisions are perfect for the bargain hunter looking for an inexpensive way to get that big screen HDTV experience. Prices continue to come down for all types and sizes of rear-projection televisions. For some examples, check out my current listing of DLP Projection TVs
Final Words
I hope that this article has given insight on some the "secrets" of rear-projection television technology that will enable consumers to make their buying decisions in a more informed manner.
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