Why does the color yellow look like white? It really does. It is so pale. When I look at both off in the distance, they are sometimes indistinguishable. Why is this? And does it have anything to do with the fact that it is close to white hot on the spectrum?
BTW I first noticed this as a child. But I must not be alone.
You probably know some of this already, but let’s start with the basics. The receptors in your eyes are called rods and cones. The cones are the ones that detect colors and most people have three types of cones. We generally call these cones the red, blue, and green cones, but that’s not quite accurate. The red cones for example will respond to red, yellow, green, and all the way down into the blue part of the spectrum. It’s just that their peak response is in the red section of the spectrum. And the green cones respond to blue, green, yellow, and red light (but again, their peak is in the green part of the spectrum)
Take a look at the image on this page.
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colcon.html
As this image shows, the red and the green cones overlap more in their coverage of the spectrum than the green and blue cones do. You will also note that yellow is right in the middle of this overlap between the red and green cones. Yellow light triggers the red and green cones equally, and the only difference with white light is that white light is going to trigger the blue cones more than yellow light will.
So that’s basically why yellow seems closer to white than other colors. You are triggering two out of the three cones in your eyes.
Certain types of color blindness can make yellow and white even less distinguishable. For example, if you have a deficiency or absence of blue cones, then since only your red and green cones work normally, yellow and white will both trigger these red and green cones equally and you will have great difficulty distinguishing between yellow and white.
Some shades of yellow look pale to me, but others don’t. School bus yellow for example doesn’t look at all close to white to me. YMMV (or rather your eyesight may vary).
It’s not actually that yellow looks a lot like white: If I put you in a yellow room or a white room, you’d easily be able to tell which is which. It’s that you can’t easily see detail in the boundary between yellow and white.
In the simplified RGB model of color vision, white contains all three of red, green, and blue, while yellow contains only red and green. That is to say, they differ only in the blue channel. And the blue channel of our color vision has very low resolution. So for anything that requires resolution, like reading, yellow on white is very difficult. Other color pairs that differ only in the blue are blue and black, magenta (RB) and red ®, or cyan (GB) and green (G), and all of those pairs are hard to read, too.
I am a little puzzled by one thing in your question–if a yellow object looks white to you, how do you know it is really yellow? I don’t know what you are experiencing because I have not seen something that looks white and then thought, “Oh, it’s really yellow.” Also I don’t know what you mean by “close to white hot on the spectrum”. The frequency spectrum of visible light does not have “white hot” (you can see one rendering of the spectrum in engineer_comp_geek’s link). What we perceive as white is actually a “white noise” of light, which is a random mix of light frequencies.
There is not just one “yellow.” The human eye can distinguish about a million different colors and we would probably classify a whole lot of them as “yellow.” Walk into a paint store and ask to see samples of “yellow” and you will spend an hour there. Some of them are quite pale, and under certain circumstances the brain might be fooled into thinking they’re white.
Vision is not just what frequencies the eyes see. The brain plays a huge role in what we see. Our brain unconsciously compensates for changes in lighting to try to correctly interpret what we are seeing. If you have a white sheet of paper and look it in open sunlight, at sunset, in a darkened room, or under a tungsten light bulb (which has a slightly orange color), it will still look white even though the frequencies reaching your eyes are different in each of these situations. This is similar to what a digital camera does to manage “white balance”–determining what color is supposed to be true white based on what colors it is actually seeing.
Chromatic adaptation is the term for this. It’s also kind of interesting, as when I color correct photos, I have to take breaks every 30 minutes or so to sort of “reset” my eyes and brain. There have been times when I’ve worked for a few hours straight correcting, say, a wedding, only to wake up the next morning and notice my color balance shifting slowly over the course of the edit as my perceived “white point” moves. (So I may tone a series of photos slightly warm, but then my brain adjusts to that “slightly warm” as being neutral white, so I have to keep pushing warmer and warmer for it to continue to register as “slightly warm.” Then you wake up and wonder what in the hell you were on when you were editing the photos. So take breaks, and use RGB/CMY numbers as a sanity check.)
Oh. I thought maybe you were viewing something under the cold-hearted orb that rules the night.
It’s interesting that you do that by hand. Sounds like a lot of work. I use Photoshop Elements (a cheap version of Photoshop) and just click “auto color balance,” or “correct color cast,” where you click on a point that should be white.
I don’t know a professional photographer that doesn’t color balance mostly by hand. We might start with trying to find a neutral point, but we usually fine-tune it from there. Auto Color balance – I’ve never had good luck with. It doesn’t necessarily take that long. If you have a relatively constant lighting situation, all you need to do is color balance the first photo of that sequence, and then cut & paste that color balance (and really, all other settings) to every other photo in the same lighting situation. Or you can dial in your color balance while shooting (which is what I used to do all the time when shooting JPEGs instead of raw: white balance card and all that.)
Well, there you have it. I am far from being a professional 
If you’re looking for a quick explanation of why yellow more closely resembles white than other colors, let me direct your attention to the Chromaticity diagram. You can see the effect in the 1931 diagram ( Chromaticity - Wikipedia ), but it’s even more striking in the CIELUV diagram ( Chromaticity - Wikipedia ). In both diagrams there is a “white locus” inside where the colors mix to produce white. The curve around the outside is the Spectral Locus of pure spectral colors, joined by the straight Purple Line. The closer on the diagram the color is to the outer boundary of Spectral Locus + Purple, the more saturated and more removed from white it is. (Not “darker”, though. The planar Chromaticity diagram ignores the overall intensity, which would be a third axis perpendicular to this plane)
Notice that yellow on the Spectral Locus is the closest pure color to the White Locus inside, especially in CIELUV. There’s not a lot of difference between them, which might be why you perceive them as so similar. The next closest point is light blue, which I think also can be argued to be similar to white in many people’s eyes.
I’ve always been surprised to see how small an angular region is occupied by yellow. It’s one of the primary colors, and in many artistic representations is given equal space with the other primary and secondary colors, but if you threw a dart at a CIE-Chromaticity-shaped dartboard, you’d have much less chance of striking yellow than any other color.
So what does saturation mean here? I
Missed the edit window:
So what does saturation mean here? It appears that all 3 near equal mixes of the 3 colors, green-red, red-blue, blue-green occupy a narrow area, but why is yellow so much closer to white than the other colors? Is this because of our perception, or something about those mixtures?
Basically, I’m not picking up why white isn’t in the center of the triangle other than the different sensitivities to different frequencies in our eyes.
Note: I don’t see blue all that well, those charts may look a bit different to me than most people see them. For instance, light blue doesn’t look white, it looks a lot like light green.
Hey, when they get moody, everything looks blue to them.
There’s no single color that can be called white. The different types of white are generally said to have a temperature, which roughly corresponds to the temperature of an object that glows with that shade of white. The sun has a high temperature, and so a high color temperature. Ironically, we call this “cool white” because it has a bluish cast. Lower temperatures, like a candle flame, have a lower color temperature, which is on the yellow or orange end of the spectrum.
A pale yellow is well within the range of what we’d call white if it were the sole source of illumination. Normally, we do see this as yellow because it contrasts with the more bluish light produced by the sun, fluorescent lighting, etc. Our eyes adjust to the dominant color temperatures, and other colors are seen relative to those. Sitting around a campfire, white things still look white, but in absolute terms the color would seem nearly orange. Something with a higher color temperature, like an LED bulb flashlight, will look very blue in comparison.
I don’t know why you have a hard time distinguishing yellow from white, but maybe you have learned to sometimes ignore the natural compensation your brain does. I’ve found I can do this for various optical effects but it does take mental effort.
There is a meme floating around that i cant find a link to of a black guy listening to a white woman on line explaining that brown doesn’t exist. its just orange. its kinda funny, but as for i can tell technically accurate. for reasons explained upthread.
My phone has a “night” setting that adds a slight orangy-yellow cast to everything, to make it easier to read with a white background (which will now look orangy-yellow). Except, in under half a minute, I perceive the background as completely white again. Same with the sepia color option in the phone’s eBook app.
Of course, @CalMeacham, a chromaticity diagram doesn’t actually explain the why of anything: It’s just descriptive. To the extent that “yellow looks like white”, it’s because of the way the human eye’s color response works. An alien (or even an Earthling creature whose eyes evolved differently) would have a completely different color response, and thus a completely different chromaticity diagram.
Chronos points out something quite significant here. In fact, IIRC, our visual circuitry is actually wired unevenly between the three primary colors. We detect a ratio between red and green, which is carried out at pretty high resolution. And we detect a ratio between the red-green combination (yellow) and blue, carried out at low resolution. I’m guessing perhaps red-green discrimination and yellow-blue discrimination evolved at different times. So the color yellow is not an obscure thing in this system. The OP’s question might be rephrased as “why does our sense of blue-yellow discrimination consider the yellow end of that ‘spectrum’ brighter than the blue end?”
And then we might contemplate that question in the following interpretation: The sun’s radiation peaks at the yellow end of the blue-yellow discrimination ‘spectrum’ and falls off very steeply toward the blue end; why do we see the end where our natural light peaks as the lighter end?"
You can actually explain a great many things with a Chromaticity diagram. I’ve done so frequently. I have no idea what your dismissive phrase “it’s just descriptive” means.
And we’re discussing human perception here (for which the chromaticity diagram is relevant), not some theoretical alien vision.
I’ve raised the issue of alien color vision distinct from our tristimulus vision many times, sometimes on this Board.
My point is that it’s not “human color vision works this way because of the chromaticity diagram”, but “the chromaticity diagram is this way because of how human color vision works”. What the diagram says is that yellow and white are hard to distinguish. But the OP already knew that. The question is why that is.
