LCD HDTV have always come second to plasma HDTVs when it comes to black levels and contrast ratios, especially against the all mighty Pioneer Kuro’s.
A fairly recent addition to LCD HDTVs is LED backlighting, which used individual LEDs rather than a standard, solid CCFL light. These LEDs are arranged into groups, and each group can be individually dimmed or brightened, depending on what is currently being displayed on the LCD.
This is great in theory, and to some degree in practice also, but it’s currently far from ideal. It’s great for when a quarter of the screen is showing something bright, and the orders something dark, but most images are far more complex than this, with a great mix of small dark and light elements.
For example, the very impressive Philips 42PFL9803 has 1152 RGB LEDs, divided into 128 groups of 9 LEDs. Just 128 groups to cover over 2million (1920×1080) pixels? That means each LED group covers 16,200 pixels.
If you look at the image above, you will see my point. (plasma Pioneer PDP-5090 on left, LED backlit Philips 42PFL9803 on right )The LED groups are currently far to big. This leads to a “clouding” effect. I believe that LED backlighting systems can be, and hopefuly will be far improved by making these groups much smaller, or even no groups at all, and every LED individually controlled, to give the LED backlight effectively a higher resolution.
If each LED was individually controlled, on a 1152 RGB LED system, each one would cover just 1800 pixels, rather than the current 16,200 pixels.
Don’t get me wrong, I think LED backlighitng is great, and far improved over the standard CCFL backlight, but can be far improved from the use of smaller LED groups, or a higher “LED resolution”.