A Color Never Seen Before

It's occurred to me that if you don't have the optical equipment to target "green" cone receptors in the eye, another method might work, although maybe not as efficiently.

If you stare at an image, the color receptors become fatigued. An example is the image below, which will produce an afterimage in red, white, and blue.

A white background could be flooded with blue and red laser light at wavelengths avoiding the green sensitivity. After the blue and red are desensitized, a green laser would only affect the green receptor to produce the desired effect.

That could explain some of the different degrees of what is commonly called colour blindness.

Some people report seeing only in black and white: I had a colleague years ago who could not see the difference between the picture from a B&W TV and a colour one.

I have the opposite: I see so many colours that deciphering which category each should go in to is difficult. A sort of over sensitivity of colour vision.

This was worst as a teen, but seems to be getting better as I age. Whether that is due to me being better able to categorise or the receptors losing sensitivity is not known.

Most people with normal color vision have 3 types of cones in their eyes resulting in 3 primary colors. Rarely, usually in females, there is a fourth type. This condition is called tetrachromacy. It sounds like you may be one of those fortunate people.

https://my.clevelandclinic.org/health/articles/tetrachromacy

According to the very interesting link in Rixter's post#3, tetrachromacy (which I had never heard of prior to this) can only occur in females. I understand that you may not wish to reveal your gender, but I would certainly be interested in knowing.

Not likely to affect me, then.

I can see a difference between red and brown, but depending on the shade cannot decide which is which.

But it is usually easy enough to decipher different whites, even if I cannot tell which colours they are tinged with. Causes all sorts of issues with my wife wanting specific off white shades of paint. Tin descriptions don’t help, either.

It's interesting that photography, television and computer displays are modeled from human vision. The camera records three channels with the sensitivity modeled to the human eye. The display or photographic paper reproduces these bandwidths for the benefit of the human eye. To another species, these images would likely not look at all realistic.

Humans and primates see 3 primary colors (3 types of cones). Most other mammals only see 2 colors. But insects and birds see more primary colors. A mantis shrimp has cones for 13 colors, but it is thought that they process each color separately rather than blend them together as humans do.

"Do Humans Have Better Color Vision Than Animals?

It is true that we see more colors than some animals. Your pet dog and cat sees fewer and weaker colors. Their view of the world is made of pastel colors. However, some animals see colors we cannot. Spiders and many insects can see a type of light called ultraviolet that most humans cannot see. Other animals, like snakes, are able to see infrared light. You can use the chart below to explore what colors certain animals see and how they compare to human color vision.

COMMON ANIMALS AND THE COLORS THEY CAN SEE

"

Ref:

https://askabiologist.asu.edu/colors-animals-see

Thanks for that info!

I was surprised to see that cats are listed as seeing "two colors but weakly". I know from personal experience that cats can "see in the dark". That must mean either that they can see under much dimmer visible light conditions than humans, or that they can see some range of infrared radiation that we humans (or at least this human) can't see.

I suspect the latter, but have no evidence to validate that suspicion.

I do definitely know that cats can see red light, having teased more than one with a red laser pointer... I've never had a laser of another color at the same time as I was around a cat...

Seeing color and seeing in the dark are two different things. Color receptors (cones) are not as sensitive as rods, which are used in low light and capture all the light, not just one color. Cats also have a reflective membrane behind the retina which increases the amount of light captured by the retina.

https://www.purina.com/articles/cat/behavior/understanding-cats/cat-vision

Thanks. A good article.

I've known of cones and rods at least since high school, but only recently learned that humans have three kinds of cones, so we truly have RGB vision. I wonder if those folks who developed color TV and later color display devices were aware of that...

I'd love to see some Sensitivity vs. Wavelength graphs for both rods and cones, both to compare different humans and for other animals, and also to learn more about the sensitivity of various kinds of electronic cameras. Obviously, it would be difficult to create such graphs for animals, and hardly trivial to create them for individual humans. Surely, some individuals would have curves that extend further into the long and/or short wavelength regions of vision, compared to others.

The test equipment would have to be capable of emitting light of wavelengths above and below the supposed limits of vision, to create valid graphs.

I've been amazed at the ability of my iPhone to produce sharp images under low light conditions. I've had a FLIR IR camera attachment for it for a number of years, so know that it is possible to detect wavelengths longer than my eyes can see. Undoubtedly, it is also possible to detect shorter wavelengths than my eyes can see. I haven't been in a position to try it, but I understand that phone cameras can obtain images of auroras that are not visible to most humans.

I've also got a thermal camera that plugs into the phone USB. It shows what a pit viper sees.

Might explain that blue or black dress controversy that went on a while back :⁠-⁠\

...or Trump's suit at the Pope's Funeral!