Posted: Wed Apr 21, 2004 5:18 pm
Chromus' answer was easier to understand ^_^ HE knows who he's talking to XD
Reading about the subject online, we find that the additive system doesn't work in dyes. Red paint subtracts green and blue light and green paint subtracts red and blue light. If you mixed them, you would get a very dark yellow, since most of the color is being subtracted out. Here's a link to a page that explains it in more detail: http://www.rgbworld.com/color.htmlchromus wrote:Phred: You've touched on a very odd topic here. The problem is that there are a few groups of people who are diametrically opposed on this issue. Let's go over the basics: all the color that we see is composed of light. The red can of Coke sitting next to me looks red because red light is boucing off of it and into my eyes. Everything you see behaves in this fashion: it looks a certain color because that is the color of light that is reflected off of it. Another thing to consider is that all colors that we see can be broken down into three components: red, green, and blue. That means that everything we look at reflects some combination of red, green, and blue. The red coke can next to me reflects mostly red light, along with a little of the other two because it's not a perfect red. When you consider both of these, what Jo-Chan said is right: white light is all three colors mixed together, while black is the absence of all three. Because there is no such thing that reflects perfect white or black, we will always get varying degrees of the red, green, and blue that reflect. This also explains the RGB system used by computers. Computer monitors project light for each pixel, so each pixel needs to have a red, green, and blue value.
Art is a totally different matter. Classically, we've been told that using red, yellow, and blue paint, we can make any color. This technically isn't true. If you were to combine red, yellow, and blue paint, you wouldn't get white or black, like you would expect. You would get a sort of muddy brown. The reason art teachers like to teach that is because you can still make a wide variety of color, plus red, yellow, and blue dye was much cheaper to make and buy a long time ago, so it has stuck. Truly, there are three dyes than can be used to make any color: cyan, magenta, and yellow. That's why inkjet printers use these colors. The combination of the three produces black, and the absence of the three shows white.
So far, we have two different systems:
Light: RGB
Dye: CMY
The cool thing is that these two systems are intimately related. In light, the combination of red and green makes yellow, green and blue makes cyan, and blue and red makes magenta. This works in reverse: yellow and cyan makes green, cyan and magenta makes blue, and magenta and yellow make red. When we consider this, we can see all colors in a nice way: all the colors that we see can be expressed in the formula xr+yg+zb where x, y, and z are the amounts of red, green, and blue that we see. This way, cyan, magenta, and yellow can be seen as -x, -y, and -z. This means that for each unit cyan you add, you subtract that much red from the surface. Example: You have a bright white piece of paper. Currently, it's formula is 255r+255g+255b (I'm using the standard 0-255 system of color). You add pure cyan dye to the paper. Because pure cyan is -255r, the new formula is 0r+255g+255b. If you remember, pure green plus pure blue is cyan, so this works!
In the way I just explained it, RGB is called the additive system and CMY is called the subtractive system, named after the way they add and subtract colors.
Personally, I don't make a distinction. To me, cyan is just -red, and so on, but others disagree with me in that respect.