LCD TV Center

Cathode Ray Tube (CRT)

This is the picture tube based technology that traditional TV sets have used for years. CRTs do not have a fixed (or native) resolution, they are analogue devices. This doesn’t mean they can not display digital signals, however any digital signal must be converted to analogue in order for the TV to display the picture.

Advantages:

* Tried an tested technology. CRTs have been used for decades and are considered to have excellent durability before their picture tubes wear out. Generally a good CRT will require very little if any servicing.
* Many claim that many modern digital technologies lack the black level detail that a good CRT provides. CRTs have a higher contrast ratio that generally results in richer shadow details.
* CRT TVs are generally a lot cheaper to purchase than digital sets.
* Can be viewed in bright surroundings.

Disadvantages:

* CRTs are a lot bigger and heavier than their digital equivalents.
* In order for CRTs to display the best picture their red, green and blue images from their tubes must be perfectly converged (aligned over one another). However this can drift out of alignment over time and require user adjustment which many find annoying.
* CRTs can suffer from the dreaded burn-in. When a stationary image is left on the screen for prolonged periods of time, such as a TV station logo or a heads up display in a video game the stationary part of the image can get a shadow temporarily or permanently burnt into the screen. This is much more likely to happen with very high contrast settings. More moderate settings minimize the risk of burn-in.

Liquid Crystal Display (LCD)

A matrix of thin-film transistors (TFTs) supplies voltage to liquid-crystal-filled cells sandwiched between two sheets of glass. When hit with an electrical charge, the crystals untwist to an exact degree to filter white light generated by a lamp behind the screen.

Advantages:

* Usually are very thin light panels, which can be hung on a wall.
* Don’t suffer from burn-in.

Disadvantages:

* Typically more expensive than plasma displays of an equivalent size.
* Black levels can be quite poor.
* LCD TVs are prone to image lag. This is where a rapidly moving object has a tendency to have a ghosting effect due to the pixels not being able to shut off quick enough. This can be especially problematic when playing video games. Newer models are getting closer to eliminating this effect but they are not there yet.

Rear Projection DLP

This projection TV technology was developed by Texas Instruments, which is based on their Digital Micromirror Device (DMD) microchip. Each of these chips has hundreds of thousands of swiveling mirrors which are used to create the image.

Advantages:

* Not susceptible to burn-in issues.
* Smaller and lighter than CRT equivalents.
* Excellent brightness and picture.

Disadvantages:

* Really needs low ambient light levels in the room when viewing a DLP TV. Not recommended for viewing in a bright sunny room. Settings can be adjusted for ambient light levels but a dark room is really required to get the best out of these TVs.
* DLPs contain a lamp that must be replaced every 6000 - 8000 hours (roughly - there are other factors that effect this). These lamps are quite expensive at several hundred dollars a piece. These lamps are considered a consumable and are not covered in warranties. If you watch TV for many hours a day you really need to factor this cost into your purchasing decision.
* Some people are susceptible to seeing a rainbow like shadowing effect on DLP televisions, especially where there are scenes with highly contrasting dark and light aspects. Newer DLP TVs with 3 chips have greatly reduced this problem. I own an older one chip DLP and have never experienced this problem.
* Poor off-axis viewing. Picture is significantly poorer when watching from an angle, especially vertically.

Liquid Crystal on Silicon (LCoS)

Similar to LCD, consists of a liquid crystal layer which sits on top of a pixelated, highly reflective substrate.

Advantages:

* Not susceptible to burn-in.
* Generally excellent brightness and color quality. Black levels considered to be very good.

Disadvantages:

* Still quite expensive compared to LCD and DLP rear projection sets.
* Like LCD and DLP rear projection sets the lamp must be replaced as necessary.

Plasma TVs

Plasma TVs consists of hundreds of thousands of individual pixel cells that allow electric pulses to excite rare natural gases (usually xenon and neon), causing them to glow and produce light. This light illuminates the proper balance of red, green, or blue phosphors contained in each cell to display the proper color sequence from the light.

Advantages:

* Can be viewed from angles and still retain excellent picture quality.
* Thin and light, can be hung on a wall.
* Excellent colour, detail and brightness.

Disadvantages:

* Significantly more expensive than rear projection digital sets.
* There seems to be more variation in the quality across the range of makes and models of plasma sets. The gap between the best sets and some of the cheap ones can be pretty high.
* Plasma TVs are less energy efficient than other technologies.
* Plasma sets are susceptible to burn-in. Similar to CRTs (above), moderate contrast levels can reduce this risk greatly, but it’s still an issue.

Front Projection Systems

Front projections systems comprise two components a projector and a screen. The projector must be placed in front of the screen to projects it’s image. Typically a projector will be mounted to a wall or ceiling above and behind the viewing position.

Front projectors, like rear projection systems, come in three main flavors CRT, LCD and DLP. For truelly massive screen sizes (>2 meters) front projectors are the only real option for home theatre enthusiasts.

Advantages:

* Capable of scaling picture size to suit your needs. The only option for very large screen viewing.
* Low footprint. The projector itself is quite small and typically ceiling mounted and out of the way. Some screens are retractable and need only be opened when using them.

Disadvantages:

* Lamp life is very short, typically only 1000 - 4000 hours depending on the type.
* Really need a darkened room to properly view the picture produced by projectors.
* If ceiling mounted may need to be professionally installed.

About the Author
Jof is the owner of Digital TV Spot. More of his articles can be found there.