Im always confused by RGB. I learned that if you want orange, you mix red and yellow. If you want green, you mix blue and yellow, if you want purple, you mix red and blue.
How is it that computers need green and not yellow?
Light vs pigment.
Computers use light, where the primary colors are Red, Blue and Green. Paint is in pigments, where the primary colors are Red, Yellow and Blue.
Just to clarify, with pigments (subtractive color mixing) the primary colors are in reality cyan, magenta, and yellow, which is why printers use CMY (and K, which is black). Blue and red are kinda close to cyan and magenta though, so those are sometimes stated as the primary colors along with yellow even though that’s not exact
Technology Connections has a couple interesting videos on the subject. Here’s one focused on the color brown with an explanation of additive vs. subtractive color (mixing light vs. pigments) starting around this timestamp. There’s also this video with some cool demonstrations using RGB LEDs and some common household objects.
Computer screens emit light, so when your computer shows a green LED next to a red LED, both green and red light wavelengths are sent to your eyes, and your brain interprets this as yellow. This is because your eyes only have red, green, and blue receptors in them, so sending green light mixed with red light is indistinguishable from pure yellow light.
Pigment, instead, works by absorbing light. The trick is that red, yellow, and blue are not the primary colors of light–it’s instead Cyan, Magenta, and Yellow (which look similar to Red, Yellow, and Blue). Yellow pigment absorbs blue light, magenta pigment absorbs green light, and cyan pigment absorbs red light. Therefore, if you mix yellow and cyan pigments together, the resulting mixture absorbs the blue AND red light, so green is the only wavelength left that gets reflected back and picked up by your eyes.
I found a video on it that explained this well with a neat diagram: https://youtu.be/YtH9eXWuf3Y?t=44
Computers make yellow with red + green…
Btw the three colour channels, red, green, blue each have 8 bits, 2^8 = 256. And for all three channels there are 256 x 256 x 256 = 16,777,216 permutations of possible colours.
If you have a Mac you can use Colour Picker (in Applications/Utilities) to hover over your screen and see the channel mixes of colours under the cursor.
White light has all the different colors in it - that’s why a prism or water drops can make a rainbow by making the different colors come out at slightly different angles. When you have, say, red paint, it’s reflecting the red light and absorbing all the rest. Same for any other color. So when you mix paint, you’re mixing stuff that absorbs different parts of the light, the more different ones you’re mixing in the more you’re absorbing. Mix all the colors and you get a dark grey going on black because it’s absorbing most of the light.
But with computers, you’re not mixing things that absorb light, you’re mixing the light itself. If you mix all the colors of light together, you get white (like doing the reverse of making a rainbow). So the formulas for making colors are kind of inverted from mixing paint.
It’s just the concept of additive color mixing vs subtractive color mixing.
Adding pigments together will ultimately create black. While adding more light together will ultimately make white.
With pigments you’re taking away from the color space. You paint red to subdue all other colors except for red.
But you use red light to make sure red is better seen.
It’s kinda cool (to me at least lol) how literal the terms “additive” and “subtractive” for color mixing are. With additive mixing (such as on a computer screen), you start with black and add the primary colors (RGB) in different combinations. If you add all of them you get white.
Subtractive mixing (like pigments) starts from white and “subtracts” those same RGB colors. You can think of cyan, magenta, and yellow as “minus red”, “minus green”, and “minus blue” respectively, since that’s which wavelengths thise pigments absorb. So mixing cyan and magenta for instance gives you “white (RGB) minus red minus green”, which leaves only blue.
Just like those districts I’ve never been to!
Also how did the “o” from the word “color” in my title make its way to the end of the sentence? 😂
FYI on lemmy posts are fully editable, including title!
Black magic
If you want to fix it, there should be an edit button behind the 3 dot menu under your post heading which will allow you to put that ‘o’ back where it belongs.
You moved an image in Microsoft word 3 years ago.
Basically there are two color models, additive and substractive. RGB is additive - turning on red it triggers the red receptors in the eye. If you turn on all three it triggers all your color receptors and you’ll see white. That is all the visible spectrum, if you look at the Sun (which you shouldn’t) you perceive it as white even if the maximum of the emission is at green.
When mixing paint (subtractive model, like CMYK on printers) if you mix all colors, they absorb different part of the light and don’t reflect anything visible for you, and you’ll see black(ish)
