Relationship Between Color/Gray Scale and Subpixels

Active matrix liquid crystal displays have a backlight within the screen which supplies the display with light. These cold cathode florescent lamps, usually located at the bottom of notebook screens, are coated with red, green and blue phosphors.

An LCD screen is covered with thousands pixels. Each pixel is divided into three subpixels. Individual subpixels display red, green and blue color filters. The color representation is based on the additive color system, meaning each subpixel of the LCD screen has the colors red, green and blue. When all three colors are turned on within the pixel, the image is seen as a white display.

The red, green and blue color filters have a spectral transmittance and it’s ideal if the backlight spectrum and color filter transmission peak match. This will achieve optimal and efficient color rendering on screen.

Color Filter Arrangements

Most liquid crystal displays have color filters that are patterned in a vertical manner, coinciding with the subpixels on the TFT array. This can achieve high performance for computer displays, but are not the best option for color mixing because of the vertical outlay.

RGB Stripe

RGB Diagonal

RGB Triad

There are other color filtering arrangements that can be used like RGB diagonal and RGB triad, which can offer better color mixing. RGB triad offers the highest performance available for video, but doesn’t function as well on the TFT array.

Amount of Color

The amount of color that a color filter arrangement can have depends on the number of grey levels within each color. An analog data driver allows for the number of colors to be endless.

Full color displays have an 8-bit gray scale, while high-definition televisions have up to 10-bit gray levels.

Capacitive screens also offer a high clarity display than that of a resistive touch screen.

Bits Supplied By Data Driver		Number Of Gray Levels		Number Of Colors
1	→	2	→	8
2	→	4	→	64
3	→	8	→	512
.		.		.
.		.		.
.		.		.
8	→	256	→	16,777,216
10	→	1024	→	1,073,741,824

As you can see, the number of greys & colors which can be produced grows exponentially in relationship to the number of bits supplied by the data driver. In fact, the forumlas are rather simple. The number of greys and the number of colors for x supplied bits can be represented by the following equations:

g(x) = 2^x
c(x) = 8^x

Back To Resource Center

Shop with peace of mind. We are D&B Rated, and BBB Reliable.