CRT:

CRT displays (Cathode Ray Tubes) use a sealed vacuum tube with the screen at the front and an electron gun at the rear. The gun fires electrons at the screen in a series of passes drawing the image onto the screen. CRTís still deliver the best quality picture available, and the image they produce can be viewed clearly at almost any viewing angle. In addition, their brightness and contrast ratios exceed that of other types of displays. They are also relatively inexpensive. The drawbacks to CRT televisions are that they are heavy, and take up more room than Rear Projection or Plasma displays. Their screen sizes are also limited to around 40î.

Rear Projection (RPTV):

RPTV sets are a great alternative to the standard CRT, since they take up less room and can have very large screens. RPTVís project the image onto a mirror which reflects it back onto the screen. This greatly reduces the cabinet depth of the unit, and allows for much larger screen sizes. RPTVís can be either analog or digital depending on the projection method. There are 3 main types of projection methods CRT, LCD, and DLP. CRT uses standard Cathode Ray Tubes just like a direct view TV set, they can produce a bright, detailed image, but are heavier and take up slightly more room than LCD, or DLP. The LCD method passes a powerful light source through transparent LCD chips. The image displayed on the chips is then projected through a magnifying lens, and then onto a mirror, which reflects the image onto the display screen. Rear Projection sets using LCDís tend to take up less room than those using CRTís, but usually cost slightly more. Also, the image produced by the LCD panels is made up of individual pixels which get enlarged when projected onto the screen. If you sit too close to one of these sets you will see what is known as the ìscreen door effectî, as the pixel structure is often visible at close range. DLP is the latest and greatest of the projection technologies. It stands for Digital Light Processing, and uses micro-mirrors to reflect colored light onto the screen. Because the light is reflected rather than passed through the chips as with LCD, DLP projectors produce images whose contrast and color saturation can rival that of CRT based systems. They do this while retaining the compactness and light weight of LCD systems. Of course they are not cheap, but the cutting edge of technology never is. Brightness and viewing angle are among some of the most important factors to consider when looking at RPTVís. When measuring brightness, you want to compare the intensity of the image emanating from the screen, not the brightness of the projected image inside the cabinet. The intensity of the image will always be less, so make sure you are comparing apples to apples when looking at brightness specs. Contrast ratio (the ratio between light and dark areas of the image) should be in the neighborhood of 1000:1 If this figure is too low, the picture will look dull, and blacks will appear to be gray.

Plasma/LCD:

Plasma/LCD displays are the most versatile when it comes to shoe-horning a large screen into a small room. Plasmas are usually less than 4î thick and can be hung on the wall if so desired. They provide an image by passing a high powered light source through cells which consist of two layers of glass between which neon-xenon gas is trapped in a plasma state. The gas is then electrically charged and reacts with phosphors which produce the colors on the screen. LCD screens work by shining a light source through an LCD chip which produces the image. Though both Plasma and LCD screens can produce beautiful, sharp, color rich images, their contrast suffers slightly due to the fact that a bright light is passing through the pixels. Blacks appear to be a very dark shade of grey, when compared to the true deep blacks that only a CRT can produce. One big advantage Plasma displays have over RPTV and LCDís is viewing angle. A plasma screen has about a 170 degree viewing angle (as good as a CRT), where as RPTVís and LCDís typically are less. Recently, LCD displays have made tremendous strides in improving their off-axis viewing angles. Although they are still not as good as a plasma or CRT, depending on your room configuration, this once important factor may now be less of an issue.