How They Work

“The LED TV vs The LCD” I recently got an email in which a reader wanted me to differentiate between the two technologies; LCD Vs LED! Many times we hear of new terminologies emerging on any given technology. In the recent past, we have had lots of technologies in as far as the Television or TV display is concerned. We had the likes of the Cathode Ray Tube, a.k.a. CRT, Plasma, LCD and then LED; what is all this halo boo about? LED TV is a bit of a contradiction but as manufacturers and retailers continue to use the term, it makes its way into the public conscience and is worth deliberating on the differences. LED televisions are really just LCD televisions that use LED lights for back lighting instead of the fluorescent CFL lighting traditionally used for LCDs. Both employ the liquid crystal diode (LCD) technology front panel containing the “twisting crystals” which delineate LCD technology. Much as the LED and LCD Tvs are similar, they cost quite differently. A 33” LED could go for something close to US$1,000 while its LCD counterpart goes for around US$400. What contributes to the variance? LED TVs feature two main forms of back lighting, edge lighting and local dimming. Edge lighting has LEDs around the edge of the panel and this allows for extremely thin construction. Lately, through advancements in LED (light emitting diode) technology these lights can be manufactured in very small sizes so even local dimming back lighting LED TVs can have a very thin depth. Local dimming backlighting features banks of LED lights behind the panel and these banks can be controlled to lower the amount of back lighting in dark areas of the screen and raise it in bright areas for higher contrast and better blacks. This is accomplished through varying features options in the TV. One recent example had an option to turn the local dimming option on or off. We did notice an improvement in black levels with the feature on. LCD panels create dark tones by blocking the backlight passing through the panel; this method of displaying black has been a problem inherent in the technology. Local dimming LED back lighting presents a solution to this problem by dimming the back light in areas where the screen should be dark. Edge lit LED will have brighter whites than most fluorescent back lit LCDs but do not have the control over the backlighting like local dimming TVs do. This comparison has become muddied lately with some LCD TVs showing very concentrated black levels. Local dimming LED TVs have been the best in the past. The main advantage of Local dimming LED TV technology has both contrast and black levels; and the other is that, Some recent LCD TVs use Edge Lit LED. With white LED backlights the difference between the two technologies isn’t very significant, but with RGB coloured lights or a colour wheel to affect the backlight colour the LED TVs have an advantage in displaying realistic colour. The main advantage on the White backlight LED TVs and LCD TVs with fluorescent backlight is nearly equal in colour accuracy. Coloured backlight LED TVs trump both. (to be cont’d) eddie@afrowebs.com