From X-Rays to Black Holes And All The Colors In Between.

The image shows two cicles. The outer is labelled RGB and the Inner is labelled CMYK. Outside the circles is a the label Invisible color.
To understand colour you need to understand that colours get darker as they move to the center of the gamut.

Color is one of those things that drive those new to graphic design up one wall, across the ceiling and down the other wall. The common complaint is “That color just isn’t what I expected.” This is especially common when one designs a print project on a computer. It is not uncommon to see some radical colour shifts between the design on the screen and the final printed page. So what is going on?

The answer to that question is not as complex or techy as you may think.

It has everything to do with gamut.

To understand this term, you need to first step back and understand that color is nothing more than light. Pure white light is all of the colors in the spectrum- for the sake of this piece we will assume the colors are Red, Green and Blue - added together. When there is no light the colour is black. These colors are the Additive colours and they are emitted colour meaning there is a light source such as the sun, your computer monitor or a flashlight involved. When a light source hits an apple, the colour of the apple is the result of the colours being reflected back to us. Those colors not used are absorbed by the apple.

The colours of print -  house paint, ink, oil paints  and so on-  are artificial colors. In the case of print, the colors are Cyan, Yellow, Magenta and Black or CMYK. (The “K” is used because using a “B” could be misinterpreted as Blue, not Black.

) These colours make colour by subtracting a part of the visible spectrum. Where there is no colour, the surface shows through. This also explains why they are regarded as the Subtractive colours. If you were to keep mixing in the inks eventually the colors would get darker and darker to the point where you have black.

These two dissimilar models actually intersect. If you were to shine Red , Green and Blue lights on the wall, you will see Cyan, Yellow and Magenta appear where the light intersects. Where the Red and Green lights intersect, for example, you will see Yellow.  At the intersection of Red and Blue is found Magenta and Cyan is found at the intersection of Green and Blue.

When I try to explain this to my students, they have a hard time creating mental models to interpret the Subtractive and Additive models. Which brings me to a method I learned when I sat in on a Canon Color Printing seminar about 20 years ago. It involves the gamut of colour.

To start let’s put all of the colour known to man in a box. In the center of that box is a black dot. I usually tell my students that do it a black hole. As we know from physics everything, including light, that hits a black hole is sucked in.

I then draw a circle around the black hole and another larger one around that first circle.

Outside that outer circle is light in the invisible spectrum. This would include such things  X-rays, Gamma Rays, Ultra Violet and Infrared.

As you move into the outer circle the visible spectrum, or gamut, takes hold and is composed of all of the possible colors that can result from adding together Red, Green and Blue light.

For those of you wondering, there are 16,777,216 individual colours encompassed within that circle. This is the common 24-bit color you use every day on your computer. There are 256 possible values for each color and, if you do the math (256x256x256), you will understand why it is your monitor displays millions of colors. As I tell my students, the beauty of this is you are “painting with light”.

The inner circle is the CMYK gamut which has, roughly, 1,000,000 colours in its gamut. This is artificial color and is created by mixing together Cyan, Magenta and Yellow pigments. The Black is added to make colours even darker.

Which brings us back to the first paragraph of this piece and that graphic artist wondering why the cool colors on the screen changed when printed. As you move from the edge of the box to that black hole, colors get darker.