The Question Of Advertising Companies

The question of advertising companies

“Do you want it in RGB or CMYK”?

This is one of the most repeated questions in any advertising or design agency. But what is RGB or CMYK? And, since we are, how does the human eye receive and perceive color? Let’s start at the beginning:

What is color?

The color itself is electromagnetic radiation in which each color has a different wavelength, and depending on it, we perceive one color or another.

And how do we perceive color and light?

The human eye has in its back what we know as cones. Cones are the photosensitive cells responsible for “reading” each wavelength and deciphering it in its color. There are three types of cones: those that interpret the color red, those that interpret green, and those that do so with blue.

As you can see, we are already talking about RGB, which stands for “red, green, and blue”. And it is a color model resulting from additive synthesis. “What?” Read!

Additive synthesis

Well, when we talk about additive synthesis we refer to the mixture of colors as light radiation. Imagine three lamps with red, green, and blue bulbs. If we turn them on and match them on white support, we would see something like this:

They are the three primary colors of light, and the mixture of them generates the cyan, magenta, and yellow colors (CMYK). We add “K” to add black, which if we get thin, is actually the absence of light and therefore color. There can be no color without light. The mixture of cyan, magenta, and yellow results in black. Conversely, mixing RGB results in white.

Subtractive synthesis

By referring to CMYK, we are switching to another color model: subtractive synthesis (pigments or dyes). Subtractive synthesis does not mix light radiation, but absorbs some and reflects others. Let me explain it briefly:

A wall painted green and illuminated by a white light, we will perceive, effectively, green. But it doesn’t really emit green radiation, because that would be an additive synthesis. Think that if we did, we would not need it to be illuminated and we could see the green wall in the dark. Subtractive synthesis absorbs, not mixes. That is, in our case, the green wall would absorb some of the wavelengths that make up white light and reflect those that we interpret as green. And… equilicuá!

Thus, red, green, and blue are the primary colors of additive synthesis, and their mixture generates three secondary colors, cyan, magenta, and yellow, which are the primaries of subtractive synthesis. And vice versa! 

So, can you summarize it for me quickly and clearly?

To understand it better, digital media use additive synthesis or RGB color mixing as light irradiation, while physical media such as a magazine or a painting are interpreted as CMYK or subtractive synthesis as a result of pigment mixing. And we, humans, when looking for example at the television (digital = RGB) or a picture (physical = CMYK) we get a wavelength that the cells (cones) located in the back of the eyes, interpret, and decipher in their corresponding color.