TV Types Explained

By Brooks Flynn Product Specialist, Philips Consumer Electronics

If you have been to your local Best Buy lately, you know there are a number of different types of TVs with varying cost and characteristics. How are you supposed to know which one is right for you? In this ESPN HD update, we will try to help you out by going through the basics of different TV technologies and the advantages and disadvantages of each. There is no flawless technology and no technology that is perfect for every type of room.

First off when you set out to purchase a TV, you should figure out what room it is going in and where you want to place it in the room. Room conditions can have a big impact on what type of TV you will want to purchase. Get an idea of ambient light in the room (are there a lot of windows/does the room get a lot of sunlight), where the windows are placed in relation to the TV (behind, on the side, directly across), and what kind of lights will you have on when you watch the TV. Having an idea of these things will help to make sure you are happy when you bring your new TV home.

CRT/Tube TV: This is what most people think of when you say TV. This has been the TV standard since the 1940's, and is therefore the most developed technology. These TVs offer many great qualities but their older technology also offers some style and size drawbacks against newer competing technologies. These TVs typically have bright images with good contrast and detail. They are available with the traditional convex (curved) screen, or the newer flat screen. Flat screens generally offer better reduction in glare from windows and less picture distortion, but if there is a window directly behind your seating position beware because you will most likely see the glare from it no matter what kind of TV you have. This TV technology is capable of displaying HD depending on the set. But the large majority of the CRT/Tube sets on the market are analog and cannot handle the HD signal. Disadvantages to this technology are that it is very bulky, heavy, and screen size is limited due to these factors. The largest standard screen size available is 36", although there some select 40" sets around. These size sets can be upwards of 250lbs, so make sure you are planning to put it on something sturdy.

RPTV/PTV: Rear Projection or Projection TV. This type of TV offers customers very large size screens, up to 65 inches and above, although there are several distinct disadvantages with this technology. RPTVs have limited viewing angles. While great strides have been made in this area, there is still a sweet spot on these TVs, meaning that sitting directly in front of the TV produces a bright image, but that bright image fades the farther away from the sweet spot you sit. Generally, positions off to the side of the TV have a greatly reduced picture brightness, and often frustrate many consumers. RPTVs are also prone to a problem know as burn-in. Burn-in is a result of keeping static images on the screen for extended periods of time. The projection elements of the TV produce very bright, very hot, images on their surface in order to project a bright image onto the screen. When left for a period of time, a static image can actually burn onto the CRT's so that the static image will always appear on the screen, often as a faint "ghost". The drawback to this then is that these TVs are not recommended for video game systems. Video game systems often leave "status bars" on the screen, and these static images can lead to burn in very easily. RPTVs are very capable at displaying HD images, but a consumer will need to verify HD compatibility with a sales representative before finalizing their TV purchase. RPTVs do have advantages over other technologies. These TVs are great for large rooms, and home theater environments. These TVs function very well in low light levels, making them perfect for dark theaters and basements. RPTVs are relatively cheap compared to other technologies for the size picture they offer.

Plasma: Plasma Flat Panel TV. This type of TV has become very popular in the last few years, thanks mostly to its stylish design and large screen sizes. Plasma panels use individual cells of gas to excite phosphor colors and produce an image. Typically these TVs are around 4 inches deep and have screen size up to 60". Like LCD Plasma TVs have some unique mounting options with many people choosing to mount them to a wall much like a picture frame or a fine painting. Plasma TVs produce a very bright and crisp image. There is no image distortion as this is a fixed pixel display (LCD, Plasma, and Micro Display are all fixed pixel technologies). So in a fixed pixel display, horizontal lines are horizontal, and vertical lines are vertical. There is no bowing as can be present with CRT Tube and RPTV TVs. These TVs are great for home theater applications, and for standard TV watching in high focal points in the home. Plasmas do have some disadvantages though as they are susceptible to burn-in from static images, so they are not very good for video game systems. Plasma panels have also been a costly option although that cost is quickly eroding as more and more plasmas are hitting the market. One item to beware of when buying plasma though is that they are not all capable of displaying HD content. You must be aware of the native resolution of the display. There are many cheaper plasma panels out there with resolutions of 640x480 and 852x480 that are not capable of displaying true HD content. These panels will take a HD signal and down convert it to standard progressive resolution meaning that you will loose a lot of the HD channel detail. If you are interested in a plasma panel capable of true HD resolution then look for native screen resolutions of 1024x768, 1365x768, or 1024x1024.

LCD: Liquid Crystal Display TV. LCD TVs are becoming more and more popular as style is becoming an increasingly important factor in TV purchases. LCD TVs are very thin, typically only a few inches deep, and can be mounted to cabinets or hung on a wall. LCD TVs produce bright crisp images, and are not prone to burn-in as RPTV and Plasma are. (LCD TVs do have a memory, meaning that static images will tend to 'hang' on the screen. But cycling the power to the screen refreshes the memory and removes the 'hung' image.) The two biggest limiting factors of LCD TVs are price and size. LCD TVs are expensive when compared to other technology, and that expense seems even greater when compared to the size in which most LCD screens are offered. These two factors are changing rapidly with the improvement in manufacturing techniques, costs are coming down and screen sizes are getting larger. This year there are a number of 30" and larger LCD screens on the market, and there are plans for the introduction of 50" and larger LCD screens in the near future.

Micro Displays: Micro Display TVs. The micro display TV category includes DLP, LCD, and the new LCoS technologies. The general characteristics of micro displays are that they provide large screen sizes comparable with RPTVs and they have a much smaller cabinet and weigh a fraction of what a RPTV does. These TVs typically produce very bright, sharp images, and might be good in a situation where a traditional RPTV can't be used either because of ambient light in the room, or because of size restrictions. Each technology has its own list of advantages and disadvantages so we will break them out separately.

DLP: Stands for Digital Light Processing, and is a technology developed by Texas Instruments. The chip made by TI actually has tiny individual mirrors that make up each pixel of resolution. These mirrors have a tiny hinge and actually turn very quickly to reflect light towards and away from the screen. A spinning color wheel is usually implemented so the mirrors are tilting on and off very quickly to rapidly display the entire color spectrum onto the screen and display a picture. This technology provides sharp and bright images, but often has trouble with color graduations because the mirrors have two positions on and off. So, levels of gray and colors require the mirrors to turn on and off extremely rapidly which can result in a type of video noise called dithering on the screen. Single chip DLP sets also suffer from a condition known as rainbowing. A percentage of the population is sensitive to this effect and they will see rainbows around images with high contrast. This effect comes from the spinning color wheel and is not present in 3-chip DLP models, because the color wheel is absent in that setup. A visible picture grid is present with this technology because of the physical nature of the mirrors and the electronics and hinges needed to operate them.

LCD: LCD rear projection sets again offer a very bright, crisp picture. LCD sets suffer mostly from an enhanced visible picture grid. This grid almost looks like a screen door is over the screen. This comes from the fact a fairly small LCD chip is used to produce the image, and that image is magnified greatly onto the screen. So, the inherent pixel separation of LCD technology is magnified onto the screen.

LCoS: Liquid Crystal on Silicon is a fairly new micro display technology that offers some distinct advantages in its category. The pixel grid of an LCoS chip is very small compared to the other two technologies. The result is a very smooth picture with virtually no visible grid to degrade the picture. LCoS can produce very smooth graduation scales to give you a full spectrum of color and grayscale. LCoS uses Liquid Crystal Pixels like a shutter to let any specific amount of light through. Where a DLP chip has to turn pixel on and off rapidly to try and reproduce shades of color, a LCoS chip just opens to the correct level, so it has no dithering or video noise when trying to product different shades of colors.

After going through all of the major types of displays you will probably be left to ask yourself several questions. How big is my room? How large of a screen do I want? Do I plan on using this mostly for movie watching in a dark room? Do I want to connect my video game system? Is style an important part of the television to me? What are my size restrictions (dimensions and weight)? These questions are important ones that might not have occurred to you prior to your television purchase, but answering these questions before your purchase will make sure that you make the right selection for your needs.

Brooks Flynn is a product specialist for Philips Consumer Electronics.