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Help System > Color University > How Color Spaces Work

How Color Spaces Work

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Let's look at this square and pretend!

square of a multi-color gradient that shows most colors

Pretend that the above square is showing you every color your eyes can see. (It isn't. It can't. No monitor can come close to showing you every color your eyes can see.) But, just pretend that it is.

(Note to color experts who are getting ready to fire off emails to us: We know about the CIE1931 diagram. We know about tristimulus values. We're trying to explain this whole thing to non-scientists by using something that is called a "simplified demonstration." Honestly now.)

(Back to the rest of you.) Okay, do you see how that square is taking up space on your screen?

It's color, and it's taking up space.

It's a color space! (Applause.) Let's give it a name, and call it the Human Vision Color Space (More applause.) Thank you, thank you.

Great! All is well with the world. Our Human Vision Color Space is able (*cough* no it isn't *cough*) to show you every color you can see. Let's say that you wanted to pick a particular color green, like the one in the black square:

square of a multi-color gradient that shows most colors, with a square showing a green shade

Whoa! First, we have to make sure that everyone in the world is looking at the same thing.

A color space must be a standard

A "standard" means that it's the same for everyone. It's essential that someone using our Human Vision Color Space in Adelaide will have same exact thing as someone in Amsterdam. This way, when people talk about colors, they're all talking about the same thing.

Well, let's wave our magic wand. Hear the bells? POOF! We just made it a standard! Everyone in the whole world sees, works with, and means the exact same thing when they talk about our Human Vision Color Space.

Now that everyone has the same exact Human Vision Color Space, and sees exactly the same thing at exactly the same size with exactly the same colors, we can use it to talk about color with each other in an accurate, repeatable way.

Color coordinates

Okey-dokey. Let's start using those X's and Y's you learned in high school to find that particular green color you're so obsessed with interested in. (Math teachers: wipe away those tears of joy.)

square of a multi-color gradient that shows most colors, with an X and Y axis

To locate the green color you like in the square, above, you start at the bottom left, or (0,0). Then, you move over six numbers on the X axis, and you move up 5 on the Y axis, so you're at (6,5). Behold! You've found the green you're after.

Test time: What numbers would you need to get a bright yellow? Answer: (8,8).

See? To get any color, you just specify an "X" and a "Y" and you have your color. Blue? (0,8). Red? (8,0).

Color Space Sizes

Here is the Human Vision Color Space again. Pretend it's showing you every single color your eyes can see:

Human vision color space, with title

But let's think about CMYK inks (printing inks). Did you know that no matter how you mix CMYK inks, there are huge numbers of colors you can't reproduce?

This means that the CMYK color space, or the space within which all of the CMYK colors will fit, is a smaller color space compared to the Human Vision Color Space:

Human vision color space, and the smaller CMYK color space

Do you notice that all of the really strong, bright colors ("saturated" colors) aren't inside the CMYK color space? That's because CMYK inks can't make them, and that's why a picture of a sunset in a brochure can never be anywhere nearly as beautiful as a sunset you see in real life.

Here are the two different color spaces side by side:

Human vision color space, and the smaller CMYK color space side by side

Did you notice that we made them the same size? Here's why. All color spaces have the same "X" and "Y" axes, with the same numbering system. Both color spaces have the same zero-through-eight numbering of their X and Y axes.

(Note: The actual color coordinate numbers in the real world range from 0 through 255, not 0 through 8, but bear with us...we'll get to that.)

On the next page, we'll see how everyone manages different color spaces with the same numbers.

NEXT: Same Numbers, Different Colors


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