Check out the first installment of our 4K primer, or read on to learn about what’s making pixels better in new 4K TVs.
Building Better Pixels with Wide Gamut Color
Not all pixels are created equal. Even at high resolution, pixel color quality makes the difference between a clear and muddy image. To understand how pixel color works, we’ll need to take a brief trip back to high school biology.
The human eye contains cells called rods, which detect brightness, and cones, which detect color. For now we’re concerned with color so we’ll focus on cones. There are three types of cone. Each is most sensitive to a certain wavelength of light. (They’re called S, M and L cones because they respond best to small, medium and large wavelength light.) A given color of light will activate one type of cone more than the other types. A blue tone will activate S-cones far more than M- and L-cones, while a red tone will activate L-cones the most, M-cones somewhat and S-cones barely at all.
Human color vision is made up of the possible blends of activation levels from these three types of cone. It’s often represented on a graph like this:
This is the CIE 1931 color space, and it’s standard for defining the range of color values that the average human eye can see.
But no display is advanced enough to show each one of these possible colors. (In fact, as you look at this on a computer the colors you see in the colorspace are limited by your monitor’s settings.) Each pixel in a display has a maximum value for its red, blue and green sub-pixels. When those are graphed on the color space, they create a triangle.
Inside the triangle are all the color values that the display can show. This is referred to as the display’s color gamut. Outside the gamut (the gray shape in the image above) are colors that people can perceive, but that cannot be shown on the display.
The example above shows the sRGB color gamut (standardized as BT.709), which is standard for CRT monitors and Blu-ray discs. It covers about 35% of the spectrum of possible colors. In other words, your Blu-ray can only use 35% of the possible colors that your eyes can see. Dolby colorist Shane Ruggieri has an apt analogy for working within the color limitations of current TVs: he says it’s like writing a story using only part of the alphabet.
Next generation technology will overcome this limitation. 4K/UHD Blu-ray will likely use wide gamut RGB (BT.2020). This is a significant improvement, displaying over 75% of all possible colors. Many 4K TVs will adopt this wide color gamut, too.
It’s hard to overestimate the added quality that comes with wide-gamut color, and unfortunately it’s impossible to display on screen or in print. While 4K resolution may only be visibly better on an enormous screen or at an unusually close viewing distance, wide gamut color is immediately recognizable and impressive. Seeing it demonstrated at Infocomm, we thought “this is why people will buy 4K TVs — for the color, not the resolution.”
The technology to support wide gamut color is almost here. Nanosys was able to cover 97% of wide gamut RGB with its quantum dot enhancement technology.
So the question is: does your 4K solution have what it needs to get better pixels, not just more?