The term 'LED TV' connotes a television set that employs light-emitting diodes (LED's) to produce the images on the screen.  As of this writing, however, no such TV exists because LED's in their present form are still too big for this purpose.  If at all, the giant LED displays we usually see in malls and sports arenas are the closest we have to a true LED TV.

However, Samsung has also been using 'LED TV' to refer to its new line of LCD (liquid crystal display) TV's that employ LED's to provide the backlighting required by LCD screens. Many people think that calling high-end LCD TV's as LED TV's is confusing (if not unfair), but many people also agree that it's a smart marketing move on the part of Samsung.

Liquid crystal displays are good at forming images on a screen, but they don't emit their own light.  As such, they need to be illuminated from its back side in order to work on monitors and TV's.  Conventional LCD TV's are back-lighted by cold-cathode fluorescent lamps (CCFL), which are always on. This continuous lighting causes problems in producing black areas on the TV screen. The lack of deep black in conventional LCD TV's is solved when LED's are used as back-lighting.  This is because LED's can be turned off at selected areas (a technique known as local dimming), allowing black areas to be black.

Note that some LED TV's, known as edge-lit LED TV's, are illuminated around the edges of the screen only, and are therefore incapable of local dimming to produce blacker blacks.  An advantage of edge-lit LED TV's is that they can be made extremely thin, as shown in Figure 1.

   

Figure 1.   Edge-lit LED TV's can be very thin.

   

Local dimming has a problem though - it also dims adjacent spots that do not need to be dimmed.  Because of this drawback, LED TV's don't always produce superior images compared to conventional LCD TV's.  TV experts say that LED TV's are best at showing images with many dark areas. Following this line of thought, It is funny to think that the best image produced by an LED TV is probably one that is totally black!

LED-lit LCD TV's are much costlier than plasma and conventional LCD TV's too. Because of this huge price difference, people have to fully understand what they're really buying while shopping for an 'LED TV'.  Advantages offered by LED TV's are as follows:  1) it consumes less power than other TV's; 2) it gives deeper blacks than ordinary LCD TV's (not applicable to edge-lit LED TV's) because the LED's can be turned off; 3)  its light colors are brighter because the LED's are bright when on; 4) it can have a wide range of color palette if red, green, and blue (RGB) LED's are used for back-lighting. As mentioned earlier, its disadvantages are its high cost and, in the case of back-lit LED TV's, the dimming of bright areas adjacent to black areas.

By the way, it must be pointed out that LED TV's are different from OLED (organic LED) displays.  

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