LCD and LED TV's are much alike in hardware, with the exception of the light source. They both use Liquid Crystal Display panels (millions of individual LC shutters arranged in a grid, sandwiched in between two thin sheets of glass), which block or allow light to pass through to produce images. Each shutter is paired with a colored filter to remove all but the red, blue and green portions of the light passing through them. Each shutter-filter pair produces a sub-pixel, so much so that it takes a large group to produce a single pixel (a tiny colored dot in the screen). Despite these similarities, there are several differences that affect the contrast and display qualities of both types of TV sets:
LCDs use CCFL (Cold Cathode Fluorescent Lamps) as a source of light. These are arranged at the back of the screen.
LEDs use Light-Emitting Diodes, which are arranged in three different ways - Edge lighting, Full-Array lighting and Dynamic "local dimming" lighting.
In Edge lighting, the series of diodes are arranged along the outside edges of the screen. When electricity flows in the circuit, the light from the diodes is distributed across the screen.
In Full-Array lighting, rows of diodes are arranged behind the entire surface of the screen.
In Dynamic lighting, the series of LED's arranged behind the entire surface of the screen can be controlled individually to achieve a "modulated backlight" light pattern.
Because diodes are comparatively smaller in size than fluorescent lamps, LED TV's are slimmer than LCD HDTV's, which allow for more free space.
LED TV's produce lesser heat than LCD TV's because diodes take a longer time to heat up than fluorescent lamps.
Image Quality and Energy Efficiency
LCD and LED TV's are better compared to the older generation of TV's (CRT's and Plasmas) because they produce better image quality and are more energy efficient. However, there are still distinct differences between LCD and LED TV's when it comes to both picture quality and energy efficiency. Here are some examples:
LED HDTVs consume less power than LCD TV's. LCD HDTV's use fluorescent backlights, which generate lesser light compared to the older generation of TV's (CRT's and Plasma TV's). Therefore, in order to produce a better image, more powerful lamps are needed. LED TV's use multiple diodes which consume a lesser amount of electrical energy compared to fluorescent lamps. In fact, LED TV's have around 20-30% lower power consumption than LCD TV's.
LED TV's produce images with better dynamic contrast than LCD TV's because the diodes in an LED HDTV can be controlled individually, allowing for dimming control. The first versions of LCD TV's had very poor overall image quality because the screen could not properly produce fast moving images and had muddy color detail.
LED HDTV's offer a wider color gamut (a subset of colors) because the diodes used in an LED TV can produce colored lights as well, in contrast to an LCD TV's fluorescent lamp that can only produce white light.
LED HDTV's produce less environmental pollution than LCD TV's. This is due to the heat emission of the devices when they are turned on. Since it takes a longer time for diodes to heat up than fluorescent lamps, LED TV's are more energy efficient than LCD TV's.
Basically, LED TV's are newer versions of LCD TV's. The change in the usage of the backlighting was made to answer the problems that the older versions of the LCD technology faced.
Jeff is a technophile whose unbiased and authentic HDTV Reviews are a big help for anyone looking to get a great deal on an HDTV. Take a look at HDTVzen.com for TV Reviews and check out the LG HDTV Reviews to help you make a good buying decision.
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