LCD Projectors vs DLP Projectors

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LCD v DLP projectors
by Kenny Hemphill


If you’ve been thinking about buying a home theater projector and read reviews or done a little bit of research, you’ll be aware that there are two technologies competing for the contents of your wallet.

Both LCD and DLP are used in projectors suitable for home theaters, but they work in quite different ways and produce slightly different results. If you ask around – particularly in electronics stores, you’re likely to be provided with a mass of information that’s confusing and often just plain wrong. So here, in an effort to clear the fog surrounding projectors, is our guide to LCD v DLP.

LCD

LCD projectors have three separate LCD panels, one for red, one for green, and one for blue components of the image being processed by the projector. As light passess through the LCD panels, individual pixels (or picture elements) can be either opened or closed to either allow light to pass through or be filtered out. In this way the light is modulated and an image projected on to the screen.

LCD projectors have historically had three main advantages over DLP. They produce more accurate colors (due to the three separate LCD panels), they produce a slightly sharper image (although this is as good as undetectable when watching movies) and they are more light-efficient, which means they produce brighter images using less power.

However, LCD projectors also have some disadvantages, although as the technology improves these are becoming less and less relevant. The first of these is pixelation, or what’s known as the screen door effect. This means that sometimes you can see the individual pixels and it looks as though you are viewing the image through a ‘screendoor.’ The second historic disadvantage of LCD v DLP is that LCD doesn’t produce absolute black, which means that contrast is less than you would get with DLP.

However, the advent of higher resoltion LCD projectors (particularly ‘HD-ready’ projectors which have a horizontal resolution of 768 pixels or greater) means that pixelation is less of a problem than it used to be. And the improved ability of LCDs to produce high-contrast images is also allowing them to be taken more seriously by home theater enthusiasts.

DLP

Digital Light Processing (DLP) is a technology developed by Texas Instruments and it works by projecting light from the projector’s lamp onto a DLP chip, made up of thousands of tiny mirrors. Each mirror represents a single pixel and directs the light projected onto it either into the lens path to turn the pixel on or away from it to turn it off. Most DLP projectors have only one chip, so in order to reproduce color, a color wheel consisting of red, green, blue and sometimes, white filters is used. The wheel spins between the lamp and the chip and changes the color of the light hitting the chip from red, to green, blue. Each mirror on the DLP chip tilts towards or away from the lens path depending on how much of a particular colour light is required for that pixel at any given instant.

The key advantages DLP has in the LCD v DLP debate is that DLP projectors tend to be smaller and lighter, have better contrast, and don’t suffer the same pixelation problems as LCD projectors. There is one problem that some users report with DLP projectors, although it appears to only affect a very small number of people. Because of the way DLP works, at any given instant, the image on screen is either red, green, or blue. However, the images change so quickly, that the human eye doesn’t detect this and your brain puts the red, green and blue images together to make a complete frame of video. Unfortunately, some people can see the individual colours, and others can detect them enough to cause eye-strain and headaches. However, technology has improved significantly with the introduction of six-color wheels and faster rotation speeds. The rainbow effect should be a problem for even fewer people. The best way to find out if you’re affected is to try out a DLP projector, perhaps by hiring one, before you buy.

Technology in both LCD and DLP projectors is improving all the time. However, at the time of writing DLP still has a slight edge in the home theater market.



About the Author
Kenny Hemphill is the editor and publisher of The HDTV Tuner


Let's resolve the frequent troubles of LCD monitor Ourselves. by Willson Peterson


TFT LCD monitors are rapidly becoming shipped with new computers by default. On this page I explain you the frequent trouble of TFT monitor and how to resolve them.

No display or white screen:

If this is a new install make sure the refresh rate is not set too high. If you installed a new video card in your system make sure the refresh rate is not set too high. Under Windows, reboot the system and go into "Safe Mode" (Use F8 key on boot up) select safe mode and change the refresh rate under display properties to either 60Hz or Default. Then reboot the system and the screen will turn on. Maximum mode on 15" TFT screens is 1024x768 and maximum mode on 17" and 19" TFT is 1280x1024. Check to see if the green light is on with the external power adapter. Make sure all plugs are secure and the video cable is properly attached to the computer.

Dark screen in games:

TFT Liquid Crystal Display monitors are a unique devices that are manufactured to meet excellent picture clarity and reproduction in a native mode. Outside a native mode graphics will be darker, fine lines and text will be thicker. Native mode for 15" TFT panels is 1024x768, 17" and 19" TFT panels are 1280x1024. Most games can be configured to run at 1024x768 which should produce clean graphics.

Thick text:

As described above, TFT LCD monitors perform best in their native modes. Other modes can be used however the reproduction of text will vary in thickness depending on the mode the monitor is running in. Best text reproduction is view in the monitors native mode.

Faint or unseen text:

TFT monitors are Bright! So bright that sometimes text in a DOS program may be very faint or not seen. In order to see this text, you can reduce the contrast level down until the text is visible. TFT LCD monitors were manufactured to perform in a GUI environment such as Windows, Linux (X) and Macintosh. Older designed programs may have upgrades to enhance this effect to make the text legible.

Wavy lines on the screen:

In some instances you may encounter wavy lines on the screen. These are usually 1/4" thick and move in a vertical motion. This is caused by a noisy electrical feed from a wall outlet. If you change your vertical refresh rate under display properties to 75Hz this effect should disappear.

Small dot on screen:

TFT panels by their very nature are difficult to manufacture. KDS uses displays from various suppliers including; Samsung, Hyundai and Acer, who all guarantee the display to be 99.99% free from pixel defect. What that means is a 15" LCD display can have up to about 6-10 broken pixels and still be considered "acceptable". Broken pixels are individual pixels, which are stuck on, off, or as one particular color. Depending on their location and intensity, they can be next to invisible or obvious. This is common to ALL TFT screens and is not considered a defect by the screen manufacturer.

Dark areas:

Retail TFT LCD monitor products employ the use of a single TFT backlight. This backlight is responsible to deliver full edge to edge brightness across the screen. On some models the screen may not be as bright in the center or the edges as other areas. This is due to the design the actual panel manufacture took to keep costs down so that the TFT panel is affordable for the retail environment. Prices of TFT panels vary according to added features (TV tuner, SVIDEO etc.). They also vary according to the number of backlights that are in the panel. High-bright monitors with multiple backlights can cost upwards of $2,500.00 for a 15" panel.


About the Author
Willson Peterson is computer expert and network engineer. He is the author of and "Monitor Glossary of Terms."

Click here http://www.ebookarticle.com to visit his website.