There are dozens of different kinds of “color-blindness”, which is not commonly used to mean inability to see any color, but some defect in color vision. We have four types of optical receptors (rods, and three types of cones). Each type of receptor has a frequency spectrum that it responds to. The spectra overlap. Nerves in our retina, optical nerve, and brains assimilate the data and produce “qualia” we call color.
Each of the receptor types has one or more possible genetic defects. Some defects make the receptor fail completely; others make it less sensitive. Most “color-blind” people have one or two common alleles that cause a reduced distinction between red and green.
Normally, rods don’t figure into color sensation, but in some people it may.
You might have tritanopia, which reduces ability to distinguish between blue and green. It’s generally called “blue-yellow” color blindness.
I got a 7 on that test. 15 is pretty good I think. 0 (or 1?) is perfect of course and only a few manage that. I took the same test on a different computer several months later and scored a 7 again! I’m proud of my 7
I got a 4, but it was was really time consuming to take, and I had to shuffle them around around a good bit looking for really subtle shade differences before I was satisfied enough to hit “submit”.
I got 4 the last time I took it, too (as far as I remember), but I remember being proud of that score, showing that test to several people who mostly got 0 on it (granted, these were all photographer friends of mine). I believe it was in the blue-green spectrum (the third grouping of colors) where my errors were.
No doubt it is a better test than the other one (and takes much longer to do), but it is still not going to be entirely reliable when presented online over an ordinary monitor, and will be unreliable in different respects on different monitors. The relationship between how the human visual system perceives colors and how RGB monitors produce them is far less straightforward than your argument implies.
What I find interesting about the test is that, as a person with normal colour vision, there are things I don’t see. There are several plates where a red green colour blind person would see a ‘5’ where I would see a ‘3’, but there is at least one plate where a red-green colourblind individual will see a number but a normal colour vision person will not.
Whatever color monitor I’ve been on, from the 8 bit cathodes of the 80s to present-day HD LEDs, whenever I played with the (RGB) values, a change in value of blue produced a corresponding change in the displayed color. More blue, looks more blue. Less blue, looks less blue. Same with the other values.
That’s why I believe this test of relative hue discrimination is a good one.
But only for you. If you have normal vision, the spectral response of the monitor will work exactly like this. And if you have a colour vision defect, you will also see linear changes in hue as the relative values change, but not the same qualia. What you can’t reproduce are tests for hue where the same hue qualia is reproduced from different spectral mixes. This is what the printed test plates do, and what is critical in detecting differences in spectral sensitivity in different subjects.
The age old idea that any colour can be created from a mix of the three primaries is basically wrong, and it gets quite complex from there on in.
I struggle a little bit with blue and green, but only when the light is low. I notice it most when playing board games around the dinner table.
In bright light, the pieces are clearly blue and green but in low light both colours move towards blue-green and become indistinguishable. Other colours remain distinguishable. I catch myself asking, “What colour is this?”
I clicked on that test with the plates and scored perfectly. If I have some version of colour blindness, it must be quite mild.
That’s completely normal. In dim light/darkness, the rods in the eyes are responding, and they see colors very poorly, unlike the conesin brighter light. The darker it gets, the more things look to be in shades of grays.
Grr… philosophical terms… qualia is by definition different in every person. It cannot be compared between me and you. As in, what you see may seem yellow to me, but I see red, and there is no way to compare because you call it red. And ultimately it doesn’t matter.
A more physiological term would be metamers, when two colors look the same to you, but aren’t physicaly the same. The monitor you are looking at now looks natural, but ultimately is based upon relative levels of RGB. It can sometimes reproduce natural spectra, but the monitor’s aren’t natural at all.
Color can be represented by three primaries at the photoreceptor level. By convention, these are red, green, blue, but in reality they don’t correspond to what we would consider to be these colors. Further on in our retina and in our brain, it gets way more complex, so yes, RGB cannot explain it all.
Rods are also sensitive to light that would be considered blue/green, if rods were capable of seeing color. This means they aren’t very good at seeing reds. A common phenomenon related to this is the Purkinje effect, where color A seems brighter than B in the light, but the opposite effect occurs when light is dim.
My friend Tom and I both have this issue too - everyone but us will call something “blue” that to us is clearly purple - but I get everything right on the test that’s linked to in this thread. Color blindness is rare in women anyway, so I don’t think it’s that sort of problem.
The rods do not see colors at all. Any color you see in dim light will be from the cones operating at a low level (and will happen only if the light is not very dim).
Have you tested that under different lighting conditions?
Have you tested that by putting things that everyone agrees is purple (and used different shades of purple… reddish purple, bluish purple, and in the middle purple) and putting it up against the thing which you think is purple?
I’m convinced if you do that, you’ll see the real blue-ness of the thing.
That is one view of things. Certainly not the only one.
Well, it might indicate whether or not you have a soul. That might kind of matter. (If you are right about the utter impossibility of comparing different people’s qualia, then you probably do, but I suspect that that is not a conclusion that you will be too happy with.)
