Understanding color space

- [Narrator] Before we get deeper into the printing process, I think it's helpful for you to understand some things about color space. So, what is color space? You may have seen this diagram in the past, this big rainbow toe. Well the exterior of this indicates something called Lab Color, which in essence represents what the human eye can see. You notice that there are smaller enclosures inside. Adobe RGB which is the native space of Adobe applications, is a little bit smaller than Lab color, obviously. One of the most commonly used color spaces sRGB and it's smaller than Adobe RGB.

And then there's CMYK; now an interesting thing about CMYK, it looks like it's a really small set of colors that you can work with, but notice this, there's actually a part of CMYK that extends beyond sRGB and that's when you start to get into cyan. So what does all this mean? Let's break it down. RGB versus CMYK, what's the difference? Well, RGB is colors of light, RGB stands for red, green, blue. It's a generous color gamut, wide range of colors.

That's what's used by monitors, and scanners, and digital cameras and your phone. It's what's called an additive color model. Let me explain what that means. Imagine you're in a room with white walls but all the lights are off, except for one light that's using a red gel, so you get a red spot on the wall. Then you turn on a light that's using a green gel, you can see where it's green on the white wall, but look what happens where it overlaps the light with the red gel; it actually creates yellow. Then you add a blue light, so here we have it, red green and blue, and where the blue light overlaps red, you get magenta.

Where the blue light overlaps green, you get an approximation of cyan and this is part of what I was showing you earlier in the little color toe that RGB doesn't quite contain the pure cyan that we expect for printing. This is really interesting I think, Because it's all colors of light, look what happens where all three colors overlap; white. How does cyan, magenta, yellow and black work? CMYK. It's a smaller color gamut than RGB, you saw that in the diagram.

These are basic printing process colors. It's what's called a subtractive color model. Let's look at how cyan, magenta, yellow and black work. Here's cyan on white paper, we add a spot of magenta ink, and where it overlaps cyan we sort of a purple y-blue. When we add yellow, yellow and magenta make red. Yellow and cyan make green, but what happens in the middle where we have all three colors? That's not quite black, it's really a muddy dark color, that's why we add that fourth ink, black.

So there you go, cyan, magenta, yellow and black. How do you get the wide range of colors that you see printed out of just those four inks? Well, this might give you an idea. This is one page out of a color book. At the top you can see it says 75 cyan. Every square has 75% cyan. Up the left side you'll see that it's yellow in 5% increments. 5% on the top row, 100% on the bottom. And then as you go across the top, it adds magenta in 5% increments.

When you look at it from the upper left hand corner down to the lower right, you see a nice wide range of colors and that's all accomplished with just three inks, cyan, magenta, yellow, in varying percentages. So here is a color image printed in CMYK. You can see it has a wide range of colors, but how does it attain those tones? It's with something called a halftone dot, if you can think of it as sort of a grid within each little square, you could have a different size color and that leads you to have a lighter red or a darker red and then as the colors all add up you can see that they give you this detail in this photograph.

I've made it a very hoarse halftone pattern here, but hopefully this gives you an idea of what's going on. I recommend you take a magnifying glass and look at a printed piece and you'll see these halftone dots. As white light is broken up into all of its constituent colors, what happens when it hits ink? This is why we call it a subtractive process. Cyan ink absorbs red, it reflect blue and green. Remember how blue and green overlap and make cyan? Magenta absorbs green and then it reflects red and blue.

Yellow absorbs blue, reflects red and green. And black absorbs all colors of light. This is an idealized illustration. In truth, printing pigments are not utterly pure, but this is what's going on, this is how ink gives you all of those colors. And finally, something happens when you place a printed piece in the sun. This is something I'm sure that you've seen, here's our poster, we put it in the window of a store. After several months, notice how the color changes.

Everything turns sort of purple. When you look at the two images compared, you see what's missing; it's the yellow ink. Yellow ink absorbs the most of sunlight, because sunlight is predominantly a blue color, even though you don't think of it that way. The yellow ink is the first to go. Now that you've seen all of this, hopefully you have an idea of how colors of light and colors of ink are related.