LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology

By Eric Z Goodnight on December 6th, 2010

HDTVs

With image technology progressing faster than ever, High-Def has become the standard, giving TV buyers more options at cheaper prices. But what’s different in all these confusing TVs, and what should you know before buying one?

If you’re considering buying a television this Holiday season for a loved one (or simply for yourself), it can be a big help to know what to look for. Take a look to find out what sets HD televisions apart, learn some of the confusing jargon associated with them, and see a comparison of four of the types of HDTVs commonly sold today.

HDTV versus Standard Definition

tv pixels close up

Televisions and monitors create images in the same way, illuminating combinations of Red, Green, and Blue to create single picture elements, or pixels. Different types of displays have their unique ways of doing this, but in theory, they’re all doing the same thing: creating the illusion of an image with tiny points made from combinations of various amounts of primary colors.

For years, the standard for television and home theater were Low-Def Cathode Ray Tube monitors, which in ordinary household situations would usually have a paltry 640 pixels by 480 pixels. While it was possible to create images full of detail by shooting movies with quality film stock, when it was played on low def televisions, quality could not help but be lost as high-quality film photography is forced into a low-resolution TV medium. While film photography is independent of the confinements of pixel-based video, it was impossible for consumers to view beautiful high-quality movies without purchasing copies of movie reels and setting up old fashioned theater projectors, which are also independent of resolution.

The simple answer was just to create home monitors with more and more pixels, with the modern widescreen definition at 1920 pixels by 1080 pixels. This makes each individual pixel smaller, creating images that look sharper and cleaner. However, HDTVs and computer monitors are more complicated than simply the sum of their pixels.

Important Terms to Know When Buying HDTVs

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With each subsequent generation of television, the language and buzzwords surrounding Hi-Def televisions become more and more complex. Here’s a rundown of the terms you’re likely to hear, and what each of them mean.

Contrast Ratio: A number ratio resembling 1:1 or 10,000:1, which illustrates how much difference there is between the brightest whites and the darkest black colors the screen can display. The higher the ratio, the better the contrast.

Refresh Rate: How often the display hardware will redraw (or “refresh”) the image created on the screen. Videos are made of “frames,” which are flashed on screen multiple times per frame because the Refresh Rate is faster than the Frame rate. In other words, you’ll watch the same frame multiple times in a single second, because the refresh is so incredibly fast. Refresh rates are measured in Hz, or cycles per second.

The higher the refresh rate, the better your picture will be, affecting the way fast-moving images appear, reducing blurring and improving clarity. Plasma displays usually have a much higher refresh rate, with the typical screen having a 600hz refresh rate, but LCD or LED TVs have been catching up with 60, 120, 240, or even some 480hz refresh rates available.

Pixel Response Time: Similar to refresh rate, Pixel response time is the number of milliseconds the individual pixels take to react to a refreshed image. While Refresh rate deals with the time it takes the hardware to refresh the image, response time refers to how quickly the individual pixels change color from white to black or red or green. The lower the time, the better. Better response times will also create less blurry pictures for fast moving images.

CRT: Acronym for Cathode Ray Tube, the oldest commercial model of televisions and computer monitors. Cathode Ray Tubes are not preferred by modern consumers, despite excellent picture quality, because they necessarily huge, bulky, and heavy.

LCD: An acronym for Liquid Crystal Display, an extremely common model of display, found in laptops and TVs, as well as displays on alarm clocks and microwaves. LCD is a very energy efficient way of creating color displays compared to CRT.

LED: Stands for Light Emitting Diode, a simple circuit that emits light. LED is the newer addition to the HDTV bestiary, and is the new, hip product to push on consumers.

Plasma: Plasmas use the same technology that the Fluorescent lights over your head use to light televisions. Plasma screens were the Rolls Royce of television screens for years, with LED displays only recently being pushed into the forefront.

Rear Projection: Also called RPTV, rear projection TVs are effectively projectors casting high-resolution images on the back of large screens, similar to movie theater projectors, except contained in a television unit.

Composite: The yellow video cable that connects old-fashioned analog signal into televisions. Composite connections are only low-resolution, and are not ideal for HDTVs.

Component: A cable connection splitting video into three signals, allowing for HD signal.

HDMI: The standard for digital input, HDMI is a digital connection for devices to televisions, capable of output of high-def video and audio.

DVI: The PC input counterpart for HDMI, How-To Geek has already explained the differences between HDMI and DVI.

Liquid Crystal Display (LCD) Televisions

lcd television

Liquid Crystal Displays, or LCD, were the first type of monitor to provide the smaller profile, allowing for thinner displays that provide good picture quality. While they do not have the depth of color range or high contrast ratios of CRT monitors, modern LCD TVs have a good range of color that can light up even bright rooms.

Liquid Crystals do not emit any light, and have to be backlit in order to produce bright colors. (If you’ve ever owned a first generation Gameboy Advance, you’ll understand what a non-backlit LCD screen looks like.) When an HDTV is classified as an LCD television, it usually means that it is backlit with CCFLs, or Cold Cathode Fluorescent Lamps.

Light Emitting Diode (LED) Televisions

led tv

While LED televisions are what is currently being pushed on consumers, they are not quite the breakthrough that the commercials would lead consumers to believe. LED televisions are actually LCD televisions that are lit with Light Emitting Diodes as opposed to the standard CCFLs, discussed in the LCD section, above. They do offer certain advantages, but as they are the new tech offered to consumers, they are pricier than older models, and do not necessarily have the best picture because they are newer.

CCFL-style LCD televisions and Plasma televisions use more energy than LED lights, which are extremely energy efficient producers of extraordinarily bright light. For this reason, LEDs are offered as the “Eco-conscious” alternative to Plasma and traditional LCD. They are also free of harmful chemicals like mercury.

There are two styles of LED televisions. One is called “edge-lit”, with lights set around the television frame; the other is “full-array,” with lights set behind the screen in a grid pattern. Edge-lit models reflect light into the center of the monitor, and are the thinnest, lightest models available. Since they have fewer lights inside, edge-lit LED models are cheaper compared to full-array models. Full-arrays, however, have the best contrast ratios in LED technology.

LED does not quite live up to the contrast ratios and colors Plasma displays can create, although they do have excellent image quality and contrast ratios no standard LCD screen can hold a candle to.

Plasma Televisions

plasma ball

When electric currents (electrons) are passed through positively-charged gasses (protons and neutron nucleuses) inside bulbs. This soup of electrical current and ions is called “Plasma,” and emits light (photons) at different wavelengths (colors). So what does this mean for your television?

Plasma screen televisions produce some of the best image quality consumers are likely to find. Their model is well suited for larger screens, and provides some of the best contrast ratios and colors available. Plasmas are also small profile, thin monitors, capable of being hung on walls like LCD or LED televisions. Pixel response is also a key benefit to plasma televisions; their images are rendered quickly, countering image blurring effects of fast-moving images on screen, providing clear pictures. In addition to all of this. Plasma televisions also have the widest angle viewing image, with quality constant from direct, in-front viewing to side angles, delivering a better picture to a larger crowd.

While they can provide some of the best images, Plasmas are the biggest energy hogs of modern flatscreen HDTVs. While many are Energy Star compliant, LEDs consume less power and contain fewer harmful chemicals. Eco-conscious and ethical gadget buyers may wish to consider this when buying a television. Plasmas are also more vulnerable to burned-in images than LCD/LED flatscreens if users are not as careful as they should be.

Rear Projection Televisions (RPTVs)

RPTV

The forgotten ancestor to theater televisions, RPTVs still have a lot to offer consumers. Since they are lit from the back by projectors, their contrast ratio is somewhat more limited, and their images look best in dark rooms. They are also thicker and deeper than any modern HDTV, which is usually a flatscreen to be mounted on the wall. While many modern projection televisions are thinner than older models, many consumers see this as a limitation, as space and viewing distance may be an important buying factor.

You’ll find that RPTVs are surprisingly lightweight, because they are almost entirely empty space. Moving an RPTV is a simple task, while some dense flatscreens may actually be heavier by comparison.

Because the images are projected, the cost of huge screens is similar to the cost of smaller units, with excellent picture quality and reasonably price on units as large as 82 inches. By comparison, Plasma or LED screens of that size would be so outrageously expensive, most stores would not care to carry them. Despite their shortcomings, RPTVs can deliver an excellent HD experience to the budget-conscious home theater.

3D-Capable Televisions

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Capitalizing on the current 3D movie trend, many HDTVs are including 3D-Capable hardware in their monitors. 3D Televisions and hardware are complex, confusing, and potentially very expensive. Stay tuned to How-To Geek for a complete rundown on 3D HDTVs, and what you’ll need to get 3D in your home theater.


Many readers will find that this guide doesn’t offer any clear-cut answers as to “which HDTV is better?” There is no objective answer, as each buyer will have unique needs. Video game players might enjoy the fast refresh and bright colors of LEDs, and sports and movie buffs may like the better contrast ratio and better colors available in Plasma TVs. Others still may want to recreate the theater-like experience with an enormous Rear-projection TV in a large dark room. Spend some time thinking about your own situation, and this guide can help you make a more informed decision for your own needs.

Image credit: First two images by the author, available freely under Creative Commons. Unnamed cables image by GKS, available under Creative Commons. LG TV Image by LGEPR, available under Creative Commons. Led 1 by Alessandro Vannucci, available under Creative Commons. Plasma Ball by BlazerMan, available under Creative Commons. DSCF1457 by lyrislite, available under Creative Commons.

Source: Howstuffworks.com; FirstGlimpse , July 2009 Issue.

Edit: Some helpful readers have pointed out that I had  flipped around a key feature of edge-lit versus full-array televisions. After looking back at my source, I found that its wording was confusing, and had to switch the one key fact about edge-lit and full-array televisions because I had read it wrong.

Eric Z Goodnight is an Illustrator and Stetson-wearing wild man. During the day, he manages IT and product development for screenprinted apparel manufacturing; by night he creates geek art posters, writes JavaScript, and records weekly podcasts about comics.

  • Published 12/6/10
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