I do not understand why human eye sees different colours from the LED TV/screen. Especially violet.  For example, how we get yellow color on TV. There are 3 small diodes Red, Green Blue in LED screen and when we see yellow, that means Red and green diodes are on and blue is off. This I understand, because wavelength for red approximately 600 nm, for green 500 nm and yellow in the middle, let say 550 nm. In this case 600 for red + 500 for green gives 550 in average, that is yellow. it is ok, good explanation.  But what about violet? Violet wavelength is 300 nm, We get it on TV if we combine red and blue. red is 600 nm, blue is 400 nm and in average I expect that we will see it as 500 nm green. But why we see it as violet which should be 300 nm? Anyway, we cannot get at all 300 nm if we combine red (600), green (500) and blue (400).  All wavelengths here are very approximate from the top of my head maybe +/- 50 nm or even more. Exact numbers do not matter, the main point is the idea how human eye see different colors.
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Our eyes contain 3 photoreceptor cells (cones) to perceive three wavelength ranges of light. Here is a visual representation of the wavelengths by these receptors (S, M and L).    So if we have light of 440 nm, it results in the color blue. If we have light of 540 nm, it results in the color green. If we see light of 650 nm, it results in the color red.  I think I understand our ability of the brain to mix the results of the signals of these receptors, producing colors like yellow. However, what I do not understand is how the color spectrum is displayed like this:    Given that spectrum, I would suggest that the color 'blue' is actually a mix between the receptors S and M. And the pure result of activating the S-receptor would result in the color 'purple' (I would describe the color in the left of the image as purple, right). Therefore, the receptor colors should instead be RGP (red, green, purple) instead of RGB (red, green, blue).  However, there is one problem with this which I cannot explain. How come that mixing red light with blue light also results in purple light? How is it possible that purple light can be achieved through mixing (additively) blue and red light, just as going to the shortest wavelength boundary of what we can see (from blue to ultraviolet via purple)?  So the actual problem here is:   Purple is the color at the very shortest wavelength we can see. Purple is an additive mix between what we see as red light and blue light.   That just doesn't make any sense. I don't see how our brain can possibly perceive this as being the same color. Shouldn't both purple colors actually be different colors (thus we would have a new different color for that)?  UPDATE: Pure activation of the S-cone (blue) may actually give violet instead of blue. That means that the color blue contains also a bit activation from the M- and L-cones (green and red). So then the "blue-est blue" is actually violet, not blue. This confusion originates from the RGB-system (and other sources) that assume blue as being a primary color, whereas violet would perhaps be more accurate! Further details can be found in the accepted answer.  The  may further help to understand what purple/magenta/violet really is.
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What determines the color of light -- is it the wavelength of the light or the frequency?  (i.e. If you put light through a medium other than air, in order to keep its color the same, which one would you need to keep constant: the wavelength or the frequency?)
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Background on color perception:  Due to the nature of the human eye and visual processing by the brain, there's an optical illusion that the same color will look different depending on the background.   It is known as the , illustrated below — center rectangles are identical:   Source:   An illustration  makes the effect of the background's color even more obvious:     Source:   (Note how the two upper-most colors in the second image appear the same, but are actually completely different.)    What about web design?  My question pertains to web design, specifically in this case, the color of link text on different backgrounds.  For a given color of text, how can one find the complementary color to make it appear the same on a certain background?    Let's take a look at an example for this question:  Consider my example below, with yellow text #FFF000 on the following backgrounds:    white #FFFFFF, black #000000, and grey #555555.          As expected, doesn't look the same at all. ()  How can we make it look the same on all three? Clearly, the text on the white background needs to be a darker yellow, and the one on the grey needs hue/tone adjustments. (The surrounding text will also affect it — but that's likely harder to account for.)  Can this perfect color somehow be calculated, based on the Hex, RGB or another system? That's where the crux of this question lies, as it would be much more efficient than manually approximating.
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The spectrum of the Sun as seen at sea level can be seen at  so we can see that wavelengths around green to yellow are the ones that are the most present. The human eye seems to be more sensitive to green wavelengths (around 555 nm which is plain green) compared to others: see .  However the Sun appears mostly white/yellowish.  I don't understand why. The human eye sensitivity for orange/yellow/blue is lesser than for green. Much lesser in case of red wavelength. So even though the spectrum is a continum of all these wavelengths why is the eye fooled toward white?  And why more toward yellow than green?  Thanks.
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Disclaimer: Please keep in mind that I am a young highschool student with no background in physics, this research was done in the course of an hour, and my reasoning could very well be wrong.  After a short conversation about color, I did some thinking, and read  The answer claims that there are $\infty^{\infty}$ colors   My first problem is the definition of colors, I'm going to simplify this (although it's not the same thing) as electromagnetic frequencies. This is what I mean when I refer to color in the rest of this question  The problem with $\infty^{\infty}$ colors is that the plank length exists. This causes two problems to arise with $\infty^{\infty}$. If $l_p$ is assumed to exist (as it is), this means the smallest distance in the universe is $l_p$. So, all wavelengths of light can be divided into a set, of the wavelengths produced by objects at $0^{\circ}$ Kelvin to $\infty^{\circ}$ Kelvin. According to this logic, there are simply $\infty$ colors.  Things are complicated further, when you introduce the Plank Temperature ($P_t$). $P_t$ is the theoretical limit temperature of the universe (at least for the purposes of light and color) Because an object hotter than $P_t$ will produce light with wavelengths shorter than $l_p$. This would introduce an upper limit on colors too.  Wouldn't this mean that the total number of possible colors is equal to however many plank lengths difference there is between an electromagnetic wave produced by a 0 degree object and a $l_p$ object? And therefor far less than $\infty$? Does this reasoning make sense at all?
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Kevin Warwick had a  and could sense whether an object was close or far. Evidence is accumulating that our brains can make sense of "foreign" information like sonar (consider the vOICe).  It can be assumed/hoped that artificial eyes will feed the human brain information more than the currently available spectrum (into the visual sense, not through the sense of warmth).   Infrared via carotine diet  There  to extend the human spectrum into the realm of infrared by maintaining a , but they were abandoned) when technological advances made seeing infrared easier.  Ultraviolet in aphakic patients - edited in  Some people with cataracts have their lense removed (resulting in aphakia),  leading to UV vision.     The eye represents a compromise between clear focus and breadth of spectrum. What does ultraviolet look like? Prof Stark possesses UV vision because he is aphakic in one eye and, with Professor Karel Tan, has published research on the nearest visible equivalent. His conclusion is that it looks whitish blue or, for some wavelengths, a whitish violet.   Thought experiment  A thought experiment with an extended visible spectrum seems interesting to me. It touches both on the qualia debate and cognitive science. I still hope you won't vote this off-topic, because I don't think cognitive science has the answer concerning the subjective experience of the stretched spectrum.  I can think of two main possibilities.  for reference the current (most common) human visible spectrum with wavelengths as objective baseline (from Wikimedia)    1. Our current repertoire of colors is stretched.    2. We see new colors.    Has this been debated in the literature? What is being proposed? Are (1) and (2) actually the same (more acuity = more colors)?  I think there is no expectation implicit in language (infrared and ultraviolet), but still when people want to demonstrate heat vision they often use red color and, um, well I don't know any movies about superheros with bee vision.
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I understand that light (color) is part of the electromagnetic spectrum, and that it depends on what wavelengths are reflected/absorbed. Though what property of an individual atom gives it its color? Do electrons, neutrons, and other subatomic particles have color?  Basically: What intrinsic property causes the differences between how the varying wavelengths of light are reflected at the atomic scale? Also, how do photons factor into this?
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Just what the title states; and this isn't an original question:  On full-moon, moonlight is almost as bright as mid-dawn; yet there is hardly any colour visible. This is not the case with sunlight.   I'm curious to know why this is the case.
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Here is my confusion: we can see colored light of different wavelengths: form red to violet. To my understanding, these stimuli cause a confirmational change in the photoreceptors in our eyes and results in a STP that eventually leads to an "all or nothing" action potential that sends another signal, again an all or nothing action potential through the optic chiasm to the occipital lobe and we perceive the colors as we see them.   My question is *how does this signaling work? *; How can a minor stimulus, resulting in an "all or nothing" chain of action potentials be converted into something as specific as the vision of color?   Asked another way, how does variation in a confirmational change at a receptor that results in "all or nothing" signaling lead to specific signals being sent such as colored vision ?  PS: I dont know jack about sensory physiology
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I thought it would be interesting to create a .blend that filters any regular video or image with vintage television look.   Edit: Although this question initially arose from my desire to create a vintage look, it has since been pointed out in a comment that all displays use arrays of RGB emitters, so it's not really an issue of vintage or not. How vintage it will end up looking is probably more a matter of the shape, size, and density of the emitters.  Reference images:       Upon examining the structure of screens, the most common seems to be rows of vertical RGB bars:    Here is another type which I believe is common in computer displays - circular dots in a hexagonal grid:    I have been thinking about how to make a screen in Blender that takes its input from an image or image sequence and for each frame converts the RGB value for a pixel (or region) and uses that to illuminate the red green and blue phosphors in the correct ratios so that when viewed from a distance an image is distinguishable.  Do you think this will require python scripting? I made some initial attempts modeling an array of phosphors then using a Light Path node and a Separate RGB node in Cycles but I haven't gotten very far. I would love to hear what you all can suggest.  Thanks!
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I have newest Latitude 5490 with 8th gen i7 and 16gb of RAM.  The screen of my laptop is little bit yellowish in comparison to my previous laptop (Latitude 5480).  I have updated all the drivers and tried all the conventional methods available on YouTube like :   setting different RGB in color management I have tried selecting sRGB2.1 profile. changing color setting in Intel Graphic control like contrast , hue options.   but none worked.  can anyone help me please.
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I was shooting in a gallery that used what appears to be a multi-colored projector and had difficulty shooting in that type of scene as the color was not even across the scene. The image shown below is what I mean, you see traces of green, blue, and yellow colors in the picture when it's supposed to be all white/gray as seen by the naked eye.  Why does this occur to the camera's output (DSLR or mirrorless) when shooting a scene that's lit by a projector? Is it the type of projector used? Is there a way to fix this or camera settings wise?
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The difference between page background color and progress on golden badges is so miniscule that I find it hard to see it at all. I see progress on bronze and silver badges just fine, but the contrast of gold badges is so small that I need to check numbers to know where to look.    My sight is far from perfect and I'm protanomalous colorblind, but I don't think this affects the contrast enough. Let's do the math.  Bg color   R   G   B   H    S    L page     255 255 255   0   0% 100% bronze   209 166 132  26  46%  67% silver   180 184 188 210   6%  72% gold     255 250 230  48 100%  95%   The lightness value of bronze and silver badge progress backgrounds is around 70%, while lightness of gold is 95%, which is displayed on pure white background with 100% lightness. This is probably a mistake as numbers are clearly inconsistent.  This applies to all websites, both to badges displayed directly in profiles and to the popup for choosing a badge to track.  P.S. Even if protanomaly affects the contrast, it's one of the weakest types of color blindness, so people with other types of color blindness will be affected even more. Also slight differences in contrast are very dependent on monitor settings. Almost nobody has perfectly calibrated monitors.  [Edit] While this question turned out to be a dupe, it's higher quality than the first one, has more info and more upvoted already, so I'd rather close the other way.  [Edit 2] Considering this question is  in  and the other one is , I find it counter-productive to close this question instead of the other one ().
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I remember reading that green colour makes the best contrast with colour of human skin so in post editing it is easier to remove it.   Is that the only reason why they use green backgrounds when filming movie scenes? I would think that different skin colour would contrast differently against green background, which would invalidate this theory.
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What happens when secondary colors like yellow,green and magenta are passed through a prism? Will it split into its component colors(for example yellow split into green and red)?If yes why we are observing secondary colors in the visible spectrum obtained when white light(composite light) is passed through a prism?
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Different kinds of white light have a different spectrum.  Light from a white LED will have blue at the peak intensity while white light from a CFL or something else will have a different looking spectrum.  I don't understand how this works. Shouldn't pure white light have a unique spectrum no matter what?  For example, a certain white LED's spectrum looks like this:$\hspace{100px}$.
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While explaining to my nephew about the physics of light, I told him we cannot see infrared color, and he kicked back with a very simple question: why can't we see it? I could not tell him. Is the human eye unable to sense such light or can it indeed but the brain can't understand the signal? any other reason?