“Cell to Bit”- From Pigments to Pixels

Featured Image from Shutterstock


When I explain the basic electrical components to non-engineers, I always approach it by comparing them to human anatomy. My colleague follows my method in explaining and it still never fails to younger students in order to understand what they are and how machine works. It makes sense to use human analogy since machinery function and mechanism are mostly inspired by how human body works. How microcontroller acts like brain; how camera operates like eyes; how motor operates the joint in robotics just like muscles, how bird and insects wings inspired the design of airplane wing; how the logic in programming language is similar to syntax and morphology in human language. By modifying the technologies, we might be able to modify nature for improving their health, safety and life quality. Perhaps, that is why robot nowadays becomes more realistic and human-like. Although it is still difficult to entirely imitate nature into machine, such as multiplying (engineer will be delighted to have machine can reproduce another machine) but we should be anticipated what human creativity can offer. “Cell to Bit” means how cell as the single unit for living organisms acts like how bit in computer from 0 or 1 can generate logic to operate entire machine. “Cell to Bit” is written to connect the similarity between nature-machine and explore new discoveries in nature that potentially leads to an inspiration for future technology.

The title of this part is “From Pigments to Pixels” where we will see how Chameleon and Liquid Crystal Display (LCD) color changing behave similarly. As we know, chameleon has the ability to change skin color. Pigments in chameleon skin play the majority of this function, which we will see it in more detail later. In technology, we know LCD has been widely used in monitor, in game console, in Human-Machine Interface (HMI) and many. The most sophisticated LCD provides wider range of colors that is very ideal for designer to create digital painting in complex shades. Thanks to combination of pixels. Although it may sound rhyme, Pigments are Pixels are not etymologically related. Pigments is derived from Latin “Pigmentum” and from “pingere” means to paint. While Pixel is a combination of pix from “pictures” and el from “element”. Nonetheless, we can still see how Pigments contributed to the color skin acts like how pixels contributed the color in LCD.

Pigments on Chameleon

Before we discuss further about this topic, it is important to grip the fundamental of color changing in a chameleon that is often misperceived as camouflage in most Kids cartoon. While the correct animal that uses mimicry for protection is Mimic Octopus (Thaumoctopus mimicus), chameleon changes its color skin to adapt with the surrounding temperature and to communicate with other chameleons.

Chameleon pigmentation is controlled by the skin layer so-called chromatophore. Chromatophore itself consist of erythrophore for red color, xanthophores for yellow color, iridophores for blue color and melanophores for brown color, as shown in Picture 1. Which the color that appears is triggered by heat that signals the nervous system to provide the color to cool down or to warm its body. The chameleon will turn brighter when the temperature is too hot to reflect the heat. While the chameleon will turn darker when the temperature is too cold to absorb the heat so it could warm the body.

Picture 1

When there is a change in temperature or mood (for example for mating) that requires to signal others, the nervous system sends the signal to chromatophores to expand or to contract. For example, if the the body requires to show red color, it is done by expanding the erythrophores while blocking out the other colors beneath them simultaneously, as shown in Picture 2.

Picture 2

Another example when the chameleon is on the calm state, the green color is made by contracting its erythrophores while reflecting light from its iridophores to mix with layer of somewhat contracted with yellow xanthophores, as Shown in Picture 3. In case you don’t have knowledge in basic color theory, the mixture of yellow and blue gives green color. So that is why Iridophores and Xanthophores take action to generate green color on chameleon skin.

Picture 3

Pixels on LCD

While Chameleon has pigments xantophores, erythrophores, iridophores and melanophores, LCD has (Red/Green/Blue) RGB pixels. These LCDs work just like the normal character type, but the backlight has three LEDS so you can generate any color you like. The color are composed of tiny crystal about a thousand times smaller than human hair, which acts as a filter for the white backlight and only allow light waves from selected range of visible spectrum to pass through. The basic principle, when color red appears, the corresponding sub pixel lets the red portion of light pass through and absorb the rest. The green and blue subpixels are deactivated when this happen. The color becomes yellow when red and green subpixels are activated while the blue subpixel is deactivated. Sound familiar with this mechanism?

If you see closer to your monitor (which you shouldn’t do this to modern LCD, this action is more applicable to older TV. Seeing screen in closer proximity only hurts your vision) you might see a combination of red, green and blue dots. Thanks to optical trick that make you unable to see these dots and able to perceive it into one color.

Microscopic view of 16×16 pixel portion of 128×128 pixel RGB TFT screen – grey box (right upper corner) is one RGB pixel measuring 300um x 300um. Image from ivoidwarranty

From Pigments to Pixels

The advantage of pixels in LCD is the wider variation of color, while pigments coloration is limited. This is due to the ability to provide various brightness that gives more hue and saturation. For example you have RGB were each color is 8 bits. So altogether for the colors you have 24 bits. Each color has 256 shades available so we get 256 x 256 x 256 for each color. The result is 16,777,216 colors which can be displayed. This is how many colors most monitors can display. Meanwhile pigment in chameleon skin only gives different saturation. So that gives the chameleon shade of pink, blue, orange, red, yellow, green and turquoise. 

The various color in LCD is very useful in HMI, that we can use red color to alert error, yellow for warning, green color for good and normal condition in machine. As we can see the pixel in LCD not only function like pigment in chameleon skin, but also serves similar purpose. Ladies and Gentleman, From Pigments to Pixels.

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