Let’s clarify one possible confusion. CRT Blue is generally brighter relative to CRT Green than daylight blue is to daylight green. CRT Blue is dim only in the sense that all blue is dim. Blue is dim because in daylight the output of red and green cones is summed to produce the retina’s luminance signal, but the blue cone output does not affect this detected luminance. (At night, rod outputs are substituted for R+G cones.)
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This agrees with you: Glossary about red, at bottom.
Sounds like you’re talking about unique hues? Hering said that RYGB were 470, 500, 570, and 700 nm respectively.
handprint : the geometry of color perception scroll down a few lines. Scroll down a bunch more (search for “what about unique red”), and see the graph right above that.
Please note than in a physiological color space, this may not apply. The “red-green” and “blue-yellow” axes do not correspond to colors that we would consider unique. Red is actually the most physiologically-determined color in this case.
It is hard to say for certain from your description, but it sounds as though you might have tritanomaly, which is very rare. It occurs when the peak response of the “blue” cones is shifted a bit toward longer wavelengths, so although blues and greens will still be distinguishable, they will not be as different as they are for most. It might also make the far violet darker than normal, or even invisible altogether.
Rods, incidentally, play no significant role in color vision at all. In conditions that are bright enough to see color properly, the highly sensitive rods are, essentially, all maxed out, and not doing anything for you. The rods function to give you monochromatic vision in low light, when it is not bright enough for the cones to function. I guess there must be an intermediate range of dim light where you are getting some rod and some (diminished) cone function, but I do not think the rods are contributing anything to color discrimination even then.
There is not any actual “processing” going on in the optic nerve, but you are right that a lot of visual processing goes on in the retina, over and above the mere transduction of light into nerve signals by the 4 types of receptor. Not only color processing, but also quite a bit of the work of edge detection and even motion processing is done there too, before the signal ever reaches the brain. There may be more too. After all, discovery of motion processing in the retina is fairly recent, but it has been shown (in some species, at least) that the retina distinguishes between object motion and motion of the whole image caused by eye or head motion, and that the retina can directly detect a rapidly approaching object. (Crudely speaking, one of the signals the retina can send to the brain means SOMETHING IS COMING RIGHT AT YOU! MOVE NOW!) It is hard to demonstrate these sorts of retinal processing directly in human beings, but there is no reason to think that our retinas do not do similar sorts of things.
Ah, so that’s why we have a three-dimensional color space, even though we have four kinds of receptors. I’ve wondered about that.
We were usually lowering green to get the best balance with red, and sometimes raising blue to suit individuals. This was 1970’s technology, 3 gun with RGB triads, higher res than television and most data monitors. The objective was to get satisfactory yellow variations, and the overall brightness wanted by the users. We only had an 8 color interface, so software adjustment wasn’t possible. I think the red phosphors were brighter than other displays. In addition, we were changing the aspect ratio of the screen from the design spec, which could lead to bleed and focus problems. We were going from 4:3 to 1:1 to make the pixels square. We could only get close though, around 1.2:1.
If insurance covers it, I’ll see the specialist, otherwise, I have little to gain. Apparently my father said he couldn’t distinquish between green and grey. I don’t have a way to get more detail. My brothers don’t seem to have any symptoms. My eyes are fine otherwise, even after staring at a CRTs and other displays for much of the past 40 years. Not so sure about the effect on my brain:)
I haven’t worked in graphics for a long time, and some questions have been answered since then, but there was a theory about the involvement of rods in some color vision, especially in ‘brown’ perception. No idea if that proved out in any way.
Do you have any info on various ‘illusions’? I’ve heard of explanations that include ideas like ‘cone saturation’ and ‘overload’ that sound fuzzy at best. The contrast and motion illusions may involve retinal processing. I’m sure some of them happen further down the line in the brain.
Slightly related, I’m kind of curious whether color-blind people see a picture like this in the same way someone with normal color vision does. (What I see is a cheeseburger, properly colored but the overall photograph has a red cast, as if taken with a filter).
In case you don’t want to read more about it - the image is entirely created with red and shades of grey, meaning the only physical color information is red. But the brain compensates by filling in the colors, so that you see green lettuce and yellow cheese. It’s the same way that a tinted or faded photograph (which might have an overall color cast) has okay color on its own, but if you were to compare it side by side with another one with a different cast, it’d really stick out.
I didn’t see any green or yellow. Brown is primarily red, and black isn’t a color, its the absence of light. I don’t know what was meant by white light, white contains red, green and blue. It looks like a hamburger with green and blue filtered out. I doubt my problems with blue have any effect.
As far as a color blind person goes, they would most likely see the “right” colors, although it is of course based upon their own visual system and may not correspond to a trichromat’s percept of the cheeseburger. A color blind person is not incapable of seeing red, green, or blue depending on their particular form. Their ability to discriminate is limited. In the cheeseburger’s case, it may be very possible for them to recognize “phantom” colors, depending on how different the green and red are.
Interesting. The pink card cited stays the same for me, but the green card on the left, and the purple on the right change color.
That doesn’t work for me, and I am reasonably confident that I have normal color vision. The lettuce looks gray to me, and the cheese looks the same color as the bun (I seem to be able to somehow recalibrate so I imagine it as yellow or white, but it is really pink, of course). However, a lot of these color vision tests do not work consistently online, because of the limitations of RGB monitors, and variations in their settings. It may be that under better conditions it is possible to create a much more distinct illusion of green and yellow this way.
I wonder if it matters whether you “know” that the lettuce should be green, etc. I suspect it is.
There are an awful lot of illusions, with many different mechanisms, and some of them are still not very well understood. Certainly some of them depend on retinal mechanisms and some on processing in the brain proper (or even a combination of the two). You can’t really generalize.
Incidentally, I did not mean to imply that all the motion, color, and edge processing gets done in the retina - it certainly does not - just that a significant part of it gets done there before the information is passed on to the brain for further work.
I agree with you, but I’d love to test my officemate. Being in a male dominated field, I’ve met my share of colorblind people, but never anyone like him. He calls himself red-green colorblind, and as far as I can tell, he really is blind to those colors and can see neither red nor green. As I said earlier, he can’t find a stationary, red laser pointer on a white background. To him, a bright, light green display looks yellow. One day we went to the wikipedia page on colorblindness, and he couldn’t see the numbers in either the protanopia and the deuteranopia example.
But, he picked out the tritanopia number more easily than the rest of us. The glare and the angle from which we viewed the screen weren’t optimal, causing the rest of us to stare for a bit to see it. It jumped out at him, but no matter how hard he tried, he couldn’t see the other two numbers. And in looking at plots I can tell you that the rest of us are generally better at discerning which data goes with which source, but occasionally, as with reds and purples, he gets irritated that we tell him to change the colors.
I’ve got to believe that there are those who have an advantage looking at pictures that may or may not contain camouflaged objects in a forest. And the incidence would be higher amongst those that have already been identified as colorblind. It is hard for me to believe though, that just any colorblind person would have an advantage.
I assume the tritan image you’re talking about is the “56.” I put it on both of my monitors, and it is much easier to see on the CRT. I’m sure you saw the note about how viewing it on monitors screws it up? For accurate diagnosis, color tests should always be run using paper or cardboard plates, lights, or CRT monitors connected to special video cards.
Yes and yes, but I wasn’t trying to diagnose him, we were passing time during a lull at work.
Given his inability to see a red laser on a white background, and his claim that “purple is his favorite shade of blue”, he would seem to be at least a protanope. I also know that, in addition to his not seeing either number on Wikipedia, his description of colors does not match any of those on a web site for designing computer user interfaces for the colorblind, and that he has occasionally remarked something along the lines of the deuteranope sentence on that same wiki page: “Similarly, violet, lavender, purple, and blue, seem to be too many names to use logically for hues that all look alike to him.” So, I suspect he has at least two forms of colorblindness, but whether they are both “Xnopes”, or a “Xnope” with a “Xanomaly” would undoubtedly require a doctor’s exmaination.