0:03

So, how do we solve the problem of non-uniform color spaces.

Okay, it turns out that there are

other color spaces that have been created over the years,

that are being created exactly to solve this problem.

So, these are uniform,

perceptually uniform colors spaces.

And here, I want to talk about two very popular ones,

that are very similar.

There are just small variations between the two,

that are CIE Lab and CIE Luv.

So, these are color spaces that have been

generated by the International Commission on Illumination.

So, CIE is a French acronym,

and this is the International Commission for the Illumination is very popular,

and has contributed a lot of very important color spaces.

So, Lab and Luv solved this problem by creating a color space where

mathematical distances between the points in

the space corresponds at least to some extent,

approximately two perceptual differences.

Let's focus on CIE Lab. How that would work?

There are three main channels.

There is the L channel which is the lightness.

Very similar to what we have seen before with HSV color space.

So, what used to be called V, value in HSV.

So, this is called lightness.

And it's basically the brightness,

the intensity of the color.

But here, the intensity of the color, is perceptually uniform.

Then, there are two additional channels a and b.

So, the a channel goes from one chromatic axis that goes from green to red.

And the next one b goes from yellow to blue.

What you see on the right, is a three-dimensional representation of these three channels.

So, on the vertical side you have the lightness, the color intensity.

Then, you have one axis is for blue and yellow,

and another axis for green and red.

And this color space is modeled, if you remember,

according to the opponent process color theory,

that I introduced earlier.

So, the idea is that,

the the way our brain perceives colors is according to these three axes.

So, we have color intensity,

we have green-red axes, and yellow-blue axes.

And every single color that we can perceive,

is a combination of these three independent axes.

So, these color space is nonlinear transformation of the physical measure of the color.

So, if you physically measure the wavelength of the color,

you don't get a linear mapping between

the physical measurement and perceptual measurement.

This is necessary to make sure that, as I said before,

distances in this space are perceived

uniformly and is designed to be perceptually linear.

So, now let me move onto another demo.

So, similarly to what I've done with the HSV and RGB color spaces,

I want to show you how to play with

the color space and show you the axes,

specification of values in the axes changes the color.