Let me now summarize the properties of all the color spaces that I've shown you. So, I've shown you the RGB color space, then the HSV/HSL color space, the CIE Lab and LUV, and the HCL. In this table, you see a summary of the main properties of interest of these color spaces. We started from RGB, and we saw that RGB is neither intuitive nor uniform. So it's problematic from the color specification point of view. Then we saw that HSV and HSL is very intuitive, but is not perceptually uniform, which is a problem when we are using it for visualization purposes, as we will see later on. Then we have the CIE Lab and LUV, that have the good property of being perceptually uniform, but are not as intuitive and easy to use as the HSV and HSL. Finally, the best one for our purposes is the HCL which is both intuitive, and perceptually uniform. Now, let me conclude the module by very briefly summarizing the main ideas that we covered in this module. So, we started by saying that color is at the same time very powerful, but also very easy to misuse. I presented a few examples that show you that if you don't know how to use color properly, it's very easy to make a disaster. Then we moved on to the perception part. I've shown you that the eye has three main photoreceptors. Well, there are actually a number of different photoreceptors, but those that we are interested in, and are mostly active in normal light conditions are three photoreceptors, and these are the basis for what is called the trichromacy theory. So the idea is that at the physiological, physical level of human vision, we have three receptors that are actually sensitive to three main kind of waves. These roughly corresponds to red, green, and blue. But we also saw in the opponent process theory part, that the way these signals are processed by our brain, creates a perception of color that is actually doesn't necessarily correspond to these three values, but it corresponds more to three other components. These are the level of lightness, and then two chromatic axis; one that goes from red to green, and another one that goes from yellow to blue. Then we moved on to this defining and describing color spaces. So color spaces are mathematical tools that allow us to describe colors by defining three values. I've shown you a number of different color spaces, and I've been discussing advantages and disadvantages of this color spaces. We concluded with one color space that is a combination of really important properties. Two main properties; one is the fact that it is intuitive and user bowl, and the other one is that it is perceptually uniform. Now, we are ready to move on to the new module, where we are going to talk about how to actually use color in visualization design.
