Hi Marc, I noticed that the overlap of color sensitivity curve will enable distinguishing single-wave light. However, this also narrow the color-space by decreasing the orthogonality. Hence, what I'm curious is how will the seperation of sensitivity curve affact the ability of distinguishing the full spectrum? Although the possibility resulting from a single wave seems decreased, the possibility from full-spectrum seems increased. And how will it affect the distinguishing of full spectrum? By the way, could you please kindly provide some literatures about the design of sensitivity curve? Jianjie
Sorry if my lecture wasn't clear. My old van appears black at night when illuminated by sodium vapor lamps. However, the picture here is clearly shot during the daytime. So it is not the case I talk about during my lecture; rather, it's the best picture I could find of the *real* color of my van.
So, the eyes send a 3-part signal to the brain of [rho,gamma,beta] value for each "pixel" in the eye and there are combinations of [rho,gamma,beta] values that cannot occur (since they are outside the "convex hull of the locus of spectral colors". But however, nothing stops such a signal from actually being sent to the brain, correct ? Say, through some bionic eye for example. In that case, would the brain start recognizing a 'new' color that was never perceived before ? Am curious how the brain would react to [rho,gamma,beta] values outside of this convex hull. Has there been research around this ? Can this be used to augment the human vision somehow to reduce the number of metamers ? Thanks for making your lectures free and available to everyone!
That is an insightful observation, and you are correct. I know of active academic research (not yet published) trying to discover what such sensations might be, by directly and individually stimulating the rho, gamma, or beta receptors in the human eye (not an easy task!)
Thanks Marc! I have a question about the number of the colors horseshoe crab can see. From my understanding of your teaching, the retina perceives different absorption values(or combinations of them depending on how many receptor systems it has) as different colors. In the case of horseshoe crab with one receptor, wouldn't it be that the horseshoe crab can perceive half of the wavelengths as different colors? Because among half of all the wavelengths, each wavelength corresponds to a unique absorption value. And in the case where a less intense light of lamda2 has the same absorption value as a full intense light of lamda1, maybe the crab would then see this less intense lamda2 as the same color as the full intense lamda1. In other words, this is an animal that can see different absorption values only as lights of different colors instead of lights of the same color with different intensities. Is this possible?
The key is that it cannot distinguish a change in wavelength from a change in intensity. A stimulus that changed from lambda1 to lambda2 but didn't change intensity would look the same to the crab as a stimulus that stayed lambda1 but changed in intensity.
Does that mean what the horseshoe crab see is a grayscale image? Each different intensities the crab feels, whether the intensity difference comes from different wavelengths or different intensities of the same wavelength, corresponds to a shade of gray?
Hi Marc, I have another question that keeps haunting me. From 29:15 you talked about a color reproduction system using three primaries A, B, C. And if the sum intensity of them is equal or less than 1. The color range they construct is a tetrahedron. But isn't it a more appropriate analogy to a color reproduction system on a computer screen that each primary is allowed to range from 0 to 1, i.e., (R,G,B) with each range from 0-255? And the color range they construct should be a hexahedron instead? The color range in the video seems to me like a RGB system with their sum no more than 255 for any given pair, i.e., (R,G,B) with R+B+G always
Thank you! Marc. Your videos are really helpful! I came across your applet website for the course when I was trying to figure out the theoretical foundation of Pointillism artists. I read that these artists don't actually mix paints. They break down the color they want to use into its components, whose mixture gives the desired color, and apply these components closely side by side on the canvas. And let the mixing process happens actually in the observers' eyes. This confuses me because when they break down the color they are thinking color mixing in the subtractive way(multiplying). But these components, when applied side by side, will mix additively in viewers' eyes. I'm really worried if they would achieve what they want. I found the knowledge I need to figure this out in your course! Thanks!
To the question why humans see only in a specral range between ca. 400 nm and ca. 800 nm with a maximum sensitivity in the green part of the spectrum: this is because the trees are green. We humans being basically apes are specialised in descovering food or enemies in the green foliage of the trees. We are so trimmed to the foliage and its coulour that we can better distinguish different tones (better to say wavelengths) of green than different tones (wavelengths) of, for instance, red. Despite the fact that green takes only a narrow band of the visible spectrum, whereas the red colour spreads from ca. 600 nm to 800 nm. Why is green so important for trees and, thus, for humans? This is because the Sun as a black body emitter has a maximum in the green spectral region and trees are adapted to that. (I might be wrong, but this is what I keep in my mind since my school days.) So basically, we do not need to see more rather than green + some nice colours for some ripe fruits. This would explain why we don't see anything beyond 800 nm - we just don't need it. As for UV, this high-energy radiation destroys proteins. That means that even if we had receptors for UV, they will be probably quickly worn out and we will be UV-blind anyways.
Let's say a given pair of lambdas, producing their (p1+p2=A, gam1+gam2 = B, b1+b2 = C) and another pair of different lambdas producing the same result (A,B,C), our brain would extrapolate the same '' color '' ? An animal with more cones (4 or 5) would be able to differentiate more colors in the range of 400-700 wavelenghts and it would be harder to '' trick '' him the way I describe before?
I wouldn't call it "extrapolation", and our brains don't need to be involved; our retina would see the same color for the two stimuli. These are called metamers.
![BLACK BAG - Official Trailer [HD] - Only in Theaters March 14](http://i.ytimg.com/vi/Du0Xp8WX_7I/mqdefault.jpg)
Hi Marc,
I noticed that the overlap of color sensitivity curve will enable distinguishing single-wave light. However, this also narrow the color-space by decreasing the orthogonality.
Hence, what I'm curious is how will the seperation of sensitivity curve affact the ability of distinguishing the full spectrum? Although the possibility resulting from a single wave seems decreased, the possibility from full-spectrum seems increased.
And how will it affect the distinguishing of full spectrum?
By the way, could you please kindly provide some literatures about the design of sensitivity curve?
Jianjie
His old Can around 5:00 Doesn't look black to me
Sorry if my lecture wasn't clear. My old van appears black at night when illuminated by sodium vapor lamps. However, the picture here is clearly shot during the daytime. So it is not the case I talk about during my lecture; rather, it's the best picture I could find of the *real* color of my van.
@@marclevoy Thanks for the response. I'll try to watch the video again to make sure I get it all fully.
So, the eyes send a 3-part signal to the brain of [rho,gamma,beta] value for each "pixel" in the eye and there are combinations of [rho,gamma,beta] values that cannot occur (since they are outside the "convex hull of the locus of spectral colors". But however, nothing stops such a signal from actually being sent to the brain, correct ? Say, through some bionic eye for example. In that case, would the brain start recognizing a 'new' color that was never perceived before ? Am curious how the brain would react to [rho,gamma,beta] values outside of this convex hull. Has there been research around this ? Can this be used to augment the human vision somehow to reduce the number of metamers ?
Thanks for making your lectures free and available to everyone!
That is an insightful observation, and you are correct. I know of active academic research (not yet published) trying to discover what such sensations might be, by directly and individually stimulating the rho, gamma, or beta receptors in the human eye (not an easy task!)
Marc Levoy Fascinating! Would love to read about this when it’s published. Thanks for the response :)
@@sanjay-89 Look at project #1 here: eecs.berkeley.edu/academics/graduate/industry-programs/meng/requirements/vccg
Thanks Marc! I have a question about the number of the colors horseshoe crab can see.
From my understanding of your teaching, the retina perceives different absorption values(or combinations of them depending on how many receptor systems it has) as different colors.
In the case of horseshoe crab with one receptor, wouldn't it be that the horseshoe crab can perceive half of the wavelengths as different colors? Because among half of all the wavelengths, each wavelength corresponds to a unique absorption value.
And in the case where a less intense light of lamda2 has the same absorption value as a full intense light of lamda1, maybe the crab would then see this less intense lamda2 as the same color as the full intense lamda1.
In other words, this is an animal that can see different absorption values only as lights of different colors instead of lights of the same color with different intensities.
Is this possible?
The key is that it cannot distinguish a change in wavelength from a change in intensity. A stimulus that changed from lambda1 to lambda2 but didn't change intensity would look the same to the crab as a stimulus that stayed lambda1 but changed in intensity.
Does that mean what the horseshoe crab see is a grayscale image? Each different intensities the crab feels, whether the intensity difference comes from different wavelengths or different intensities of the same wavelength, corresponds to a shade of gray?
Hi Marc, I have another question that keeps haunting me.
From 29:15 you talked about a color reproduction system using three primaries A, B, C. And if the sum intensity of them is equal or less than 1. The color range they construct is a tetrahedron.
But isn't it a more appropriate analogy to a color reproduction system on a computer screen that each primary is allowed to range from 0 to 1, i.e., (R,G,B) with each range from 0-255? And the color range they construct should be a hexahedron instead?
The color range in the video seems to me like a RGB system with their sum no more than 255 for any given pair, i.e., (R,G,B) with R+B+G always
Yes, both of your statements are true.
Thank you! Marc. Your videos are really helpful! I came across your applet website for the course when I was trying to figure out the theoretical foundation of Pointillism artists.
I read that these artists don't actually mix paints. They break down the color they want to use into its components, whose mixture gives the desired color, and apply these components closely side by side on the canvas. And let the mixing process happens actually in the observers' eyes.
This confuses me because when they break down the color they are thinking color mixing in the subtractive way(multiplying). But these components, when applied side by side, will mix additively in viewers' eyes. I'm really worried if they would achieve what they want.
I found the knowledge I need to figure this out in your course! Thanks!
To the question why humans see only in a specral range between ca. 400 nm and ca. 800 nm with a maximum sensitivity in the green part of the spectrum: this is because the trees are green. We humans being basically apes are specialised in descovering food or enemies in the green foliage of the trees. We are so trimmed to the foliage and its coulour that we can better distinguish different tones (better to say wavelengths) of green than different tones (wavelengths) of, for instance, red. Despite the fact that green takes only a narrow band of the visible spectrum, whereas the red colour spreads from ca. 600 nm to 800 nm. Why is green so important for trees and, thus, for humans? This is because the Sun as a black body emitter has a maximum in the green spectral region and trees are adapted to that. (I might be wrong, but this is what I keep in my mind since my school days.) So basically, we do not need to see more rather than green + some nice colours for some ripe fruits. This would explain why we don't see anything beyond 800 nm - we just don't need it. As for UV, this high-energy radiation destroys proteins. That means that even if we had receptors for UV, they will be probably quickly worn out and we will be UV-blind anyways.
Let's say a given pair of lambdas, producing their (p1+p2=A, gam1+gam2 = B, b1+b2 = C) and another pair of different lambdas producing the same result (A,B,C), our brain would extrapolate the same '' color '' ? An animal with more cones (4 or 5) would be able to differentiate more colors in the range of 400-700 wavelenghts and it would be harder to '' trick '' him the way I describe before?
I wouldn't call it "extrapolation", and our brains don't need to be involved; our retina would see the same color for the two stimuli. These are called metamers.
Getting hard to understand now
Thank you very much sir
Thanks unto L13