RGB and CMYK

- [Instructor] In this movie, we're going to investigate the difference between the RGB and the CMYK color models, and I thought we'd have a little bit of fun with it. Let's do a scenario, a role game in which you and two of your friends have been sent out to a world in deepest, darkest space to investigate a phenomenon that's been found there, and it's this giant black obelisk, as you can see in front of you. It's not doing anything, it's just there, but you reach out and touch it, and suddenly, all the lights go out, and there you are.

There is no light energy, total and complete darkness. Now, it just so happens that you have got a torch with you, and you turn that on, and you find out that your torch emits pure red light. And you can see in the middle where it's the strongest that the light is at maximum intensity, and that's as red as red can be. And as it falls off to the edges, it gets progressively darker. One of your friends turns on their torch, and intersects it with yours, and it turns out they've got a green torch, and again, at maximum intensity, you can just see pure green light and it falls off to the edges, getting darker.

Where the two overlap, you get yellow light, and the varying tones of falloff give you some additional colors in there as well. And your final friend turns on their torch, which happens to be blue. And you notice that when their torch crosses over with your torch, you get magenta, and when their torch crosses over with your other friend's torch, you get cyan, and in the middle, you get pure white light. The maximum combined energy of those three light sources gives you white light.

And that's how RGB works. It's an additive model where the maximum strength of all of those things added together gives you white. It's an energy-based model. If you pulled the plug out of the monitor right now that you're watching this on or turned the device off, the screen would jump back to black, no energy passing through it. So CMYK, we get transported into a different world, a world starting with white paper. And on our white paper we add some cyan, and that cyan subtracts from the reflected light that you're seeing from the paper.

And you can see it changes, and there's some cyan. And now we add some magenta, and that, again, is subtracting from the paper white. You're changing the density or the wavelength of the light as it moves through it. And where they overlap, you get blue. And when we add yellow, then mixes occur between all three, just as with RGB, but now we get green between yellow and blue, so very similar to the pigment model. We get red between yellow and magenta, and we get a blue between magenta and cyan.

And you can see it's almost the opposite of the RGB model. And in the middle, we get a weak, low-density black, and we could actually add some black ink to that to thicken that up. Okay, so you can see they're very similar, they're related, but sort of opposite. Not completely, but kind of. Let's have a look at that in a real-world printed scenario simulation. Here are four color plates, a cyan, a magenta, a yellow, and a black plate. And I'm being a bit hard on you, actually, by showing you them as they actually are, so let's introduce some color across these, so there you go.

This is a simulation, but this is the cyan, magenta, yellow, and black plates as they print. So let's put them on a piece of paper. So we get some paper, and add our cyan ink, like so, that's how that gets printed. And then we add magenta, and you can see where those two things are mixing together, and also where they're in isolation. Now we'll add the yellow plate, and you can see in places how that's approaching a weak, low-density black in a few places.

And then we add the black plate. The K, by the way, stands for key, because it keys all of the colors up, gives it a point of reference, and your eyes then interpret that as a color image. And so there you are, that's RGB, an energy-based model, additive, adding together, and CMYK, a pigment-based model that is subtracting from the whiteness you already have of the paper, and hopefully you now understand that. In the next movie, we're going to look at something called spot colors.