I recently saw an example of red-green blindness and I cannot wrap my head around how they’re able to see both yellow and blue vividly. If they can see yellow and blue individually, why can they not see green?
I did a bit of searching and learned how the red, green, and blue cones in your eyes work, so I was temporarily satisfied that it was the same as TVs and monitors that don’t actually produce the colour yellow but only give the illusion… Until I remembered that the illusion is achieved by combining red and green light, so wtf.
Help my brain. Make it simple.
In: Biology
Don’t think of it in terms of being able to “see” the colours, but rather in being able to tell them apart. People with RG colourblindness can tell yellow apart from blue because they can differentiate the presence/absence of blue light, but can’t tell you if it’s a greenish yellow or reddish yellow.
It is indeed not as simple. While the TV monitor is able to produce three distinct wavelengths of light the cones in our retina is not as selective and will dectect light in a wide spectrum of wavelengths at different sensitivities. Worst is the blue cone which in most people will be able to pick up even orange wavelengths although much weaker then blue light. Our brain perecives the color of light by looking at the ratio of signals from our cones and also our rods. This does mean that a standard monitor is not able to display all the possible colors we can see but it can give a good representation of most of them.
The problem with red/green color blindness is that without the red cones there will be some hues of red and green that excites the remaining cones exactly the same. It is not the same as just switching off the red lights of your monitor.
The colors that a monitor is able to represent are found on a visualization of the visible spectrum. Example: [https://www.thoughtco.com/the-visible-light-spectrum-2699036](https://www.thoughtco.com/the-visible-light-spectrum-2699036)
Note that it starts at red on the low wavelength side and slowly morphs to purple/violet on the other.
The way normal vision works, the wavelengths are all relatively easily distinguished. “This here is red, this is green, this is blue”
For those of us that are color blind, there are certain wavelengths that are easily confused. “This is red, this could be either red/green, this is *certainly* green, this is blue.
Getting back to the analogy of rods/cones in our eyes and the monitor. Simplifying things, let’s say we have red cones, green cones, and blue cones in our eyes. Some of our cones are defective and react to the wrong color of light.
Taking this a step further, this is how the color blindness glasses work. They don’t do anything but cut out the frequencies of light that are the most commonly confused. Now what you’re left with is light that is definitively green or definitively red.
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