Toshiba Regza LCD TV

As for LED backlit unit for LCD TV, generally speaking, RGB LEDs, rather than white LEDs, broaden "color gamut," one of the major indices of image quality. Nevertheless, Toshiba used white LEDs for its new LCD TVs, which it claims are "the highest image quality models of Regza products."

When asked why, Toshiba’s Motomura said, "In fact, image quality is higher with a white LED backlight."

He explained it as follows. First, white LED light sources are more efficient in boosting image quality because the white balance fluctuates more easily when the light source is RGB LEDs. Second, image quality becomes more likely to degrade if the color gamut is extended more than necessary because it causes the display to render incorrect colors.

It is true that RGB LED backlights offer a wider color gamut than white LED backlights, but the color reproduction range of white LEDs is sufficient to render colors of most objects, Motomura said.

On the other hand white LED back light is mch cheaper than RGB backlit unit at least 60%!

Ref.
The Above picture illustrates the comparison of image quality between Toshiba's previous LCD TV (right) and its new product (left), which combines a white LED backlight and local dimming. The LED-backlit model on the left uses a glossy panel.

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