- [Instructor] 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
is called 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,
that 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?
Well, let's break it down.
RGB versus CMYK, well, what's the difference?
Well, RGB is colors of light.
RGB stands for red, green, and blue.
It's a generous color gamut, wide range of colors.
And 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
that all the lights are off, except for one light
that's using a red gel so you get a red spot on the wall.
and then you turn on the 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.
But this is really interesting, I think.
Because it's all colors of light,
look what happens where all three colors overlap, white.
So how does cyan, magenta, yellow, and black work, CMYK?
Well, it's a smaller color gamut than RGB.
You saw that in the diagram.
These are the basic printing process colors.
It's what's called a subtractive color model.
So 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 get sort of a purpley 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.
So it's really kind of a muddy, dark color.
And 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.
So every square has 75% cyan.
Up the left side, you'll see that
it's yellow in 5% increments.
5% yellow on the top row,
hundred percent yellow on the bottom.
And then as you go across the top,
it adds magenta in 5% increments.
So 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 and yellow in varying percentages.
So here's 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.
So 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 coarse halftone pattern here,
but hopefully this gives you an idea of what's going on.
I recommend that you take a magnifying glass
and look at a printed piece
and you'll see these halftone dots.
So as white light is broken up
into all of its constituent colors.
What happens when it hits ink?
Well, this is why we call it a subtractive process.
Cyan ink absorbs red, it reflects 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 then black absorbs all colors of light.
Now, this isn't 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.
And this is something I'm sure that you've seen.
Here's our poster.
We put it in the window of a store,
and after several months, notice how the color changes.
Everything turns sort of purple.
And when you look at the two images compared,
you see what's missing.
It's the yellow ink.
And so yellow ink absorbs the most of sunlight
because sunlight is predominantly a blue color
even though you don't think of it that way.
So 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.