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Help System > Color University > Same Numbers, Different Colors

Same Numbers, Different Colors

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We've already seen that different color spaces have the same numbering system, but contain different colors:

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

This means that the same numbers will usually result in a different color, depending on what color space you're in.

Here's an example: The color (8,0) is a bright, vivid red in the Human Vision Color Space:


...but, it's a reddish orange in the CMYK color space:


Real RGB Numbers

Until this point, we've been using examples where colors are expressed as two numbers, with each number ranging from zero through 8. But, actual color numbers are (usually) specified as three numbers, with each number ranging from zero through 255.

They're called RGB numbers, for Red, Green, and Blue. Colors can also be referred to as CMYK numbers, where there are four numbers, with each number ranging from 0 through 100 (percent).

When you see our "0 through 8" numbers, just know that you're really talking about the RGB or CMYK numbers that you've probably seen when working in any image editing or drawing program. But let's stick with the "0 through 8" for now and press on.

More color spaces, comin' up!

Of course, it gets more complicated. There are many different color spaces. Here are the most common (listed inside the fictional Human Vision Color Space):

Diagram of multiple color spaces
  • The CMYK color space is the smallest: it can represent all the colors that a printer can produce when mixing cyan, magenta, yellow, and black ink.
  • The sRGB color space is a little bigger than CMYK. It can represent all the colors that most computer monitors can reproduce. This means that your monitor (or phone screen) can show some colors that can't be produced with a printer.
  • The Adobe RGB color space is even bigger. It can represent nearly all the colors that can be produced by any monitor, and it can also represent nearly all the colors that can be produced by expensive photo printers that use many colors to produce prints.
  • The ProPhoto color space is so big, that it can represent most (but not all) colors that you can see, and even some that you can't. Bizarre but true. It can represent far more colors than can be currently produced by anything that humans make. It's used by printing and design professionals who believe it's a good idea to use it.

What all of this means is that any particular color number (for example: 3,5) means a different color in each of the above color spaces!

Numbers + color space = color

As you can see, if you say you'd like to print this exact color:

Square of violet in the sRGB color space

It's not good enough to say that it's "Color (2,2)" (or, in real life: "RGB 136,38,228"), because:

Here's color (2,2) (or RGB 136,38,228) in the sRGB color space:

Square of violet in the sRGB color space

Here it is in the Adobe RGB color space:

Square of violet in the Adobe RGB color space

Here it is in the ProPhoto color space:

Square of violet in the ProPhoto color space

Here it is in the CMYK color space:

Square of violet in the CMYK color space

The takeaway? When you specify a color number (like (2,4) or RGB(103,223,8)), that's not enough. You must also know which color space you're in, so you know which exact color you mean.

Color profiles and color spaces

A color profile is simply a bunch of numbers that define a color space. It's sort of like a blueprint full of measurements for a house. The house is the color space, and the blueprints and measurements of the house are the color profile.

For example, the Adobe RGB color space is defined by an Adobe RGB color profile.

ICC profiles

(Note: an ICM profile is the same as an ICC profile. They are the same thing except with a different name. It doesn't matter if a file ends with .ICC or .ICM.)

The ICC is the name of the International Color Consortium, a group of companies that got together to write standards that ensure that colors are specified and used in very particular, repeatable ways.

When you see that a file is an ICC profile, it contains numbers that are listed in a certain order and in a certain way so that the computer (or printer, or phone, etc.) knows how to display colors correctly.

ICC profiles define and map out things like the Adobe RGB color space, or the CMYK color space, or the color space your printer is capable of producing on a particular paper.

An ICC profile can be an external file, or it can be stored inside of an image file itself, like a .PSD Photoshop file, or a .PNG image file. When you store an ICC profile inside a file, that's called "embedding" the profile in the file, or an "embedded" profile. These embedded or external profiles let the computer or printer display or print the correct colors.

Let's get a little fancier and talk about color "gamut" and printer color spaces (printer profiles). You can do this!

NEXT: Color Gamut and Printer Profiles


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