The WOW! Buzz

For the past year or a little more, some manufacturers have been producing high end sets which are billed as “LED” sets, or “light emitting diode”.  This has been a confusing distinction because all flat panel TV’s are either plasma technology or LCD (liquid crystal display) technology.  Light Emitting Diodes are those small, expensive Christmas lights, or the little red numerals on an old calculator, right?  So is that what makes the picture on these LED sets?  Millions and millions of little diode lights?

In a word, no.  Every LCD television requires a backlighting system which is on at full brightness all the time.  The millions of LCD semiconductors in a flat panel set act as “light valves” to that backlight, allowing anything from no light (black) to colors of various brightness (256 levels of brightness per color) to being completely “open” (bright white) on the screen (a bit of a simplification, but bear with me).  For most LCD televisions, the “backlight” source is a full color spectrum fluorescent lamp array running at full brightness.

What is different in an “LED” HDTV is that the backlighting system is made up of a large (white light) LED array rather than the fluorescent lamp array found in a more conventional design.  This approach has several advantages:

1) LED backlight requires much less energy to operate at full brightness–less than half the energy in most applications.

2) LED can be designed to provide a much wider spectrum of color in the source light they provide than a fluorescent light.  (Ever notice that a diamond doesn’t sparkle much under a fluorescent office lamp?  Same principle–a TV needs a “broad spectrum” white light to produce a full range of natural colors.)

3) Sets can be made much thinner and lighter vis a vis a conventional backlight technology.  Some LED driven LCD sets are just over an inch thick while most conventional LCD sets run 2.5″ to 4″ in thickness.

4) Unlike a fluorescent display, some designs of LED array can be selectively “brightness controlled” by circuitry especially designed to enhance the picture.  Remember our discussion a few months ago on contrast ratio? The tiny semiconductor “valves” of the LCD have some limitation on how black the blacks can be (with a highly energized white backlight behind them) compared with the bright areas of the picture.  Because an LED array is, in most designs, many small light devices either behind or at the edge of the LCD matrix, selective areas of the picture can be brightened or dimmed to help the LCD matrix do its job.  When properly implemented, this technique results in enhanced contrast ratio, and  in certain ambient light conditions, a visible enhancement to the picture.

These sets are higher end designs, and the price is commensurate with the high end label.  But some of these sets I have auditioned have truly stunning video quality, and bear investigation if you are in the market.

Until next time….