How does color on a computer screen work? I always thought that color was a way that light reflects on different materials/objects. How does this work on a TV/computer screen?
In: Technology
None of the answers so far cover this in ELI5 level.
There are two ways of making color. The one you’re taught in art class is pigment based. This is how light reflects from an object, including paint, clothes, crayons, etc. The primary colors are red, yellow, and blue. Red + yellow = orange, yellow + blue = green. You mix all the colors together you get brown/black (true black is hard to do).
Then there’s light-producing objects, not light-reflecting. This includes TV monitors, light bulbs, fire, and the sun and stars. For light-producing things, the primary colors are red, green and blue (RGB). Red + green = yellow, red + 1/2 green + 1/4 blue = orange. You mix all the colors together you get white. You can play around with mixing RGB colors here: [http://web.stanford.edu/class/cs101/image-rgb-explorer.html](http://web.stanford.edu/class/cs101/image-rgb-explorer.html)
There are two ways we make color, called additive or subtractive. They sound just like what they are. Additive color is how a computer screen works. Red, Blue and Green and added to black to create the color spectrum. When you are mixing paints the color are being subtracted from white. This is how a printer works, using Magenta, Cyan and Yellow. Ultimately they function same way, mixing certain amounts of each color creates all the colors we see. What you describe is the subtractive color. When you put cyan ink on a white page the ink makes the white paper absorb all other light colors and then not reflect the cyan.
TV & Computers screens do not reflect light, they shine their own light. Each pixel is a light source that can change color and brightness (or rather three sub-pixels: red, green and blue). The screen is a mosaic of such lights.
Color is just a specific wavelength of light hitting your retina. For example, a light wave with a wavelength of 530nm will appear to look “green” to you.
Most objects are *reflective*, in that they absorb some wavelengths of light and reflect others – the wavelengths they reflect are the colors you see. When the sun shines, the tree leaves look green because they absorb all wavelengths except for green, which is reflected back to you.
Other objects are emissive, in that they give off light waves. The color of light they emit will correspond to the wavelength of those waves. Older incandescent lightbulbs generally emit a yellowish-white light, which means that they emit all wavelengths but most of it in higher wavelengths, towards the red/infared portion of the visible spectrum.
With white light like this, you can filter out certain light waves with some translucent material. For example, you can make a flashlight shine red if you shine it through a red piece of glass. This red piece of glass filters out all the other wavelengths, leaving only red light to shine through.
Your computer uses LEDs in a similar fashion to light up pixels using 3 different colors. Each pixel can emit Red, Green, and Blue light, and it uses a combination of these colors to make up the image you see on the screen.
Your definition of colour is true when the light is white light like sunlight which contains all the colours
But white light is nothing but a mixture of red, blue and green light, these are the primary colours. The other colours are obtained by mixing specific quantities of these colours
On a screen there are pixels and pixels has 3 colours red, green and blue. Suppose you want to get purple colour then the red light and blue light are on but the green light is off, so red and blue mix and give you purple colour.
Your eye has three color detectors and uses their relative output to determine color.
TVs take advantage of this by *only* emitting three wavelengths that exactly match those cells, and turning them up or down to make your brain interpret the signal as different colors.
They only use blue, green, and red. The saturation or amount of each, tricks your brain into thinking it is a particular color outside of that, but it’s not. If you get really close to a screen you can see this. It is trickery and nothing more.
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