Let’s start with color vision
We know that different wavelengths of visible light have different colors. Short wavelengths are blue, and long wavelengths are red, as shown in the picture below.
Corresponding to human eyes, there are three kinds of cones, which have different Spectral sensitivity, creating Trichromacy of human eyes. In general, these three cone types are called short (S), medium (M), and long (L) cone types in order of their peak wavelength of spectral sensitivity. The normalized response spectra of S, M, and L cones to monochromatic spectral stimuli are shown in the figure below.
Roughly, L cells are more sensitive to red light, M cells are more sensitive to green light, and S cells are more sensitive to blue light.
The causes of color blindness and color weakness are related to the loss or functional defects of these three kinds of cones. For example, a loss of L cones leads to red blindness, while a defect in M cones leads to a weak green. As we have seen before, the sensitive bands of L-cone and M-cone are somewhat overlapping, so the symptoms of red and green color blindness are similar, which is generally referred to as red-green color blindness.
After a brief introduction to the causes of color blindness, let’s talk about the difference between color blind and non-color blind color systems from a mathematical point of view.
The concept of RGB must be well known to all. Then the three channels of red, green and blue are taken as the X, Y and Z axes in the three-dimensional coordinate system to obtain the spatial description of colors, which is called the RGB color space. Similarly, colors can be described in terms of the proportion of L,M, and S cones stimulated, which is called the LMS color space.
We can think that the color space of LMS corresponding to normal vision is a complete cube. Then, according to the previous introduction, the color system seen by color blind patients becomes a two-dimensional plane in the complete cube because of the functional loss of certain cones. Depending on the severity of the color blindness, the location of the plane varies, such as cutting a plane right in the middle or cutting a plane slightly at an oblique Angle.
With the math behind it, there are sophisticated algorithms to simulate what color-blind people see. For example, we used a common color-blindness test to simulate what a color-blind person might see, such as the image below
The red blind people might see something like this
A group of green blind people might see something like this
The images above are based on some sophisticated algorithms to simulate what people with color blindness would see.
According to statistics, about 6% of the world’s population is color weak, about 2% of the population is color blind, a small number of monochromatic vision (total color blindness). Red-green blindness accounts for about 8% of the global male population and 0.5% of the female population (because red-green color blindness is a recessive genetic disorder on the X chromosome). Blue blindness is rare and is thought to be acquired.color blind glasses are useful for the weak people and blind people.
Color blindness patients may encounter some difficulties in life and work, but I am glad to see that many software, game and hardware companies have launched products that have added optimization or auxiliary functions for color blindness and color weakness.