5 ms·

Perhaps a nitpick, but 256^3 doesn't really represent anything about human perception-- it's just how we store colors in computer memory. The human eye can perc

by tbabb 9y ago

Perhaps a nitpick, but 256^3 doesn't really represent anything about human perception-- it's just how we store colors in computer memory. The human eye can perceive a far wider range of colors than any screen can (currently) represent. It's just as valid (and probably more accurate) to use floating point to store color (rather than bytes), and in many high-fidelity applications this is actually how it's done. The bit about colors "looking different" in different contexts also isn't really an "extra axis". The example you give is just your brain (attempting to) separate out the illumination from the scene colors. The range of actual colors you can perceive isn't increased by this. Fundamentally human color perception is three-dimensional, because humans have three classes of color receptors on their retinas. There are also rods in the retina (the cells that are color-insensitive and detect only brightness), and in principle they could inform color perception, but this does not seem to be the case-- the intensity of light only shifts things around in the original three-dimensional space. There are also a very, very few people (women only) with genetic mutations that give them four different color receptors in their retina. However, there is no evidence that their brains can take advantage of this extra information and allow them to perceive an extra "axis" of color. It is much more likely that the "mutant" receptors are lumped in with the stimulus of one of the others, which will shift their perception of color, but not expand it. In short: There are three axes of color perception. Optical illusions don't change that.

sillysaurus3 9y ago
Optical illusions reveal that we have more than three axes of color perception. The first gif and the last photo are examples of this, and the renaissance artists had a firm appreciation of it. (See DaVinci's journals, specifically the chapters on color.) Part of the reason I want to put together this series is to rekindle this knowledge. It seems very much "lost": your comment represents the status quo of color science, but if you were an ambitious artist in 1450, you'd run experiments and determine that much of what we take as fact is actually quite a lot more complicated in practice. The eye, and especially our perception of colors, is so complicated that entire tomes barely scratch the surface. And Munsell's discoveries were only made in 1900, barely over a hundred years ago. There's still a lot more to discover. To be clear: it's true that our three receptors imply three axes of color perception. But when you assemble an image as a whole, the entire portrait results in an experience quite different than any individual color. EDIT: That the perception of color is influenced by surrounding colors is true, but that this adds a "fourth channel" is [citation needed]. One of the most important aspects of color science is that you have to be willing to believe the possibility that some strange ideas are true. In this case, I can dispel that illusion, but only if you're open minded to it: Consider a painting. Why choose a certain shade of yellow? To produce an effect. The above images demonstrate that where you put that shade of yellow causes a very different effect. Now, if you accept as an axiom that the only reason to choose a color is to produce an effect, then that means all three primary colors (red, green, blue) are different axes in your ability to cause an effect. But the fact that the arrangement of colors causes different effects means that the spatial arrangement is a fourth "lever" that you can use to change the experience. That implies it's accurate to call this phenomenon a fourth channel. (I'd post this edit as a reply, but HN isn't having it right now.) One interesting area of science to investigate is the frequency spectrum of natural images. Our brains are tuned to see certain frequencies more than others, e.g. blades of grass. And the reason colors produce different effects depending on where they are in relation to each other is to help us resolve different shapes in an image. http://web.mit.edu/torralba/www/ne3302.pdf http://web.mit.edu/torralba/www/ne3302.pdf https://www.cs.cmu.edu/~efros/courses/LBMV07/presentations/0208Gist.pdf https://www.cs.cmu.edu/~efros/courses/LBMV07/presentations/0...
- tbabb 9y ago
  The statement I take objection to is this: > The fact that colors influence colors around them means that there are far more than 256^3 viewable colors: the spatial axis is like a fourth channel. That the perception of color is influenced by surrounding colors is true, but that this adds a "fourth channel" is [citation needed].
  - just2n 9y ago
    I'm not sure I buy that it means there are more absolute viewable colors there, but rather there are merely different interpretations of the same colors. We do have fairly strong confirmation that our brain doesn't interpret color absolutely but can adjust based on luminescence (see: all examples of shadow illusions) and patterns (see: https://www.youtube.com/watch?v=mf5otGNbkuc https://www.youtube.com/watch?v=mf5otGNbkuc), perhaps that's what is meant by a "fourth channel"?
- psyc 9y ago
  I’ve referred to DaVinci as the father of CG, based on his formalizing the perspective projection. This bit about color adds to my thesis.
- roywiggins 9y ago
  The simplest example of this is that in a watercolor class I was told to make shadows bluer than the object, not just blacker. And indeed it looks much more natural than a black shadow, and I think it's this effect of juxtaposing colors.
  - tbabb 9y ago
    The sky is blue and the sun is yellow. Subtract the sun and you are left with only blue light from the sky. ...which explains why indoors, shadows /do/ tend to be colorless: http://www.camilleprzewodek.com/uploads/1/5/9/2/15923552/6393647_orig.jpg http://www.camilleprzewodek.com/uploads/1/5/9/2/15923552/639...
- dkersten 9y ago
xenadu02 9y ago
The retina itself does various forms of processing, some of which is about eliminating noise, but some of which is involved in relatively complex things like edge detection. The nerve bundles connected to the retina do further processing. The visual cortex itself does a lot of processing, then the conscious part of the brain does even more. There's recompositing and temporal correlation, motion-compensation, prediction, edge detection, lighting/shadow compensation & color perception, threat assessment, pattern recognition, object recognition, face recognition and that's just scratching the surface. Even transmission of color information isn't a simple RBG signal. It appears the eye transmits differential signals (such as B-Y) and other information as well. There are multiple layers of processing that go on in our visual system. You can't reduce it to three axes. The eye is not a camera, doesn't work like a camera, and can't be simplistically thought of as if it were a camera.
- tbabb 9y ago
  All of those things about visual processing are true. > You can't reduce it to three axes. This is my claim: It is possible to represent all possible visual stimulus with: f(direction, time) -> (a, b, c). That is what I mean by "vision is three dimensional". It is not possible to add another channel "d" to the (a,b,c) tuple which is not redundant; so anything you add would not be an extra axis or increase the dimensionality of the perception space. The brain/retina may generate lots of extra "channels" from processing this (moving) three-valued image, but those extra channels can't be stimulated independently of each other; they depend entirely on those original three degrees of freedom as a function of space and time. In that sense they aren't really "axes", because they aren't degrees of freedom. That's what I mean by "there isn't an extra channel." If you agree with that, then we don't disagree and we are just arguing semantics. :)
  - edejong 9y ago
    It’s funny that you introduce time in your equation, because it shows how your view is incomplete. In our visual system, you cannot reduce to three dimensions without creating a recursive relation. It should be more like: Ret(a,b,c)_t = f(Ret(a,b,c)_{t-1}, current_stimulus) Since it is a recurrence, we cannot reduce to three dimensions.
roywiggins 9y ago
Don't forget purple, which doesn't exist in the rainbow. It's red and blue, which average to green but we see it as purple. Which validates the three-axis idea: purple is when the red and blue axes are dominant. But it's still peculiar.
- mygo 9y ago
  'red and blue' averages into green? Yeah, that's not really how our eyes perceive light. We see the colors that we see because certain wavelengths of light stimulate certain cones in our iris, which makes our brains hallucinate in color, basically. We see green when the short-wavelength-sensitive, medium-wavelength-sensitive, and long-wavelength-sensitive cones are all stimulated. A single wavelength of light around 520nm will stimulate all of these cones and satisfy the requirement for green to be seen. In fact this is usually the wavelength of light we'll find in a green laser. But there can be multiple different wavelengths of light in combination to make the eye perceive green as well. And that's what's happening when we see purple. When we see purple (magenta), we're never, ever, seeing just one wavelength. Because as we've said, there is no such thing as a magenta wavelength. It's not in the rainbow. So take red-wavelength light, and blue-wavelength light, with the key absence of green-wavelength light, and we'll see purple/magenta. But green-cone stimulating light must be absent or we will not see magenta. It's pretty interesting how what we see is not necessarily what's out there. Another interesting one is gray. There is no "gray" on the rainbow. Any time we're seeing gray, we're actually seeing a bunch of colors at once. Which is weird because gray appears colorless. But depending on the colors present that make us hallucinate that grey, there could be as few as 3 colors or even millions. We just don't see them because they're stimulating our cones in such a way as to neutralize each other. So under natural lighting, an aluminum macbook will be grey and colorless. But walk inside a room that only has red lighting (so no white lights) and that gray colorless macbook is now a colorful red. Anyways, what we perceive has never been a literal transcription of what's actually present. The brain takes in stimuli from the outside world, but it alone ultimately decides what we see. It shows us different things under different conditions. Different lighting conditions, under the influence of drugs, colors next to other colors, light arranged in certain textures, whether we're malnourished, whether we're daydreaming with our eyes wide open, whether we've just finished staring at an intensely bright light or a colored wall and are now looking at something else, all of it influences the colors that we actually end up seeing. The brain always has the final say in what we perceive, not the outside world. We're basically hallucinating 24/7, all the while thinking what we see is what actually is.

by tbabb 9y ago

sillysaurus3 9y ago

Optical illusions reveal that we have more than three axes of color perception. The first gif and the last photo are examples of this, and the renaissance artists had a firm appreciation of it. (See DaVinci's journals, specifically the chapters on color.) Part of the reason I want to put together this series is to rekindle this knowledge. It seems very much "lost": your comment represents the status quo of color science, but if you were an ambitious artist in 1450, you'd run experiments and determine that much of what we take as fact is actually quite a lot more complicated in practice. The eye, and especially our perception of colors, is so complicated that entire tomes barely scratch the surface. And Munsell's discoveries were only made in 1900, barely over a hundred years ago. There's still a lot more to discover. To be clear: it's true that our three receptors imply three axes of color perception. But when you assemble an image as a whole, the entire portrait results in an experience quite different than any individual color. EDIT: That the perception of color is influenced by surrounding colors is true, but that this adds a "fourth channel" is [citation needed]. One of the most important aspects of color science is that you have to be willing to believe the possibility that some strange ideas are true. In this case, I can dispel that illusion, but only if you're open minded to it: Consider a painting. Why choose a certain shade of yellow? To produce an effect. The above images demonstrate that where you put that shade of yellow causes a very different effect. Now, if you accept as an axiom that the only reason to choose a color is to produce an effect, then that means all three primary colors (red, green, blue) are different axes in your ability to cause an effect. But the fact that the arrangement of colors causes different effects means that the spatial arrangement is a fourth "lever" that you can use to change the experience. That implies it's accurate to call this phenomenon a fourth channel. (I'd post this edit as a reply, but HN isn't having it right now.) One interesting area of science to investigate is the frequency spectrum of natural images. Our brains are tuned to see certain frequencies more than others, e.g. blades of grass. And the reason colors produce different effects depending on where they are in relation to each other is to help us resolve different shapes in an image. http://web.mit.edu/torralba/www/ne3302.pdf http://web.mit.edu/torralba/www/ne3302.pdf https://www.cs.cmu.edu/~efros/courses/LBMV07/presentations/0208Gist.pdf https://www.cs.cmu.edu/~efros/courses/LBMV07/presentations/0...

tbabb 9y ago
The statement I take objection to is this: > The fact that colors influence colors around them means that there are far more than 256^3 viewable colors: the spatial axis is like a fourth channel. That the perception of color is influenced by surrounding colors is true, but that this adds a "fourth channel" is [citation needed].
- just2n 9y ago
  I'm not sure I buy that it means there are more absolute viewable colors there, but rather there are merely different interpretations of the same colors. We do have fairly strong confirmation that our brain doesn't interpret color absolutely but can adjust based on luminescence (see: all examples of shadow illusions) and patterns (see: https://www.youtube.com/watch?v=mf5otGNbkuc https://www.youtube.com/watch?v=mf5otGNbkuc), perhaps that's what is meant by a "fourth channel"?
psyc 9y ago
I’ve referred to DaVinci as the father of CG, based on his formalizing the perspective projection. This bit about color adds to my thesis.
roywiggins 9y ago
The simplest example of this is that in a watercolor class I was told to make shadows bluer than the object, not just blacker. And indeed it looks much more natural than a black shadow, and I think it's this effect of juxtaposing colors.
- tbabb 9y ago
  The sky is blue and the sun is yellow. Subtract the sun and you are left with only blue light from the sky. ...which explains why indoors, shadows /do/ tend to be colorless: http://www.camilleprzewodek.com/uploads/1/5/9/2/15923552/6393647_orig.jpg http://www.camilleprzewodek.com/uploads/1/5/9/2/15923552/639...
dkersten 9y ago

xenadu02 9y ago

The retina itself does various forms of processing, some of which is about eliminating noise, but some of which is involved in relatively complex things like edge detection. The nerve bundles connected to the retina do further processing. The visual cortex itself does a lot of processing, then the conscious part of the brain does even more. There's recompositing and temporal correlation, motion-compensation, prediction, edge detection, lighting/shadow compensation & color perception, threat assessment, pattern recognition, object recognition, face recognition and that's just scratching the surface. Even transmission of color information isn't a simple RBG signal. It appears the eye transmits differential signals (such as B-Y) and other information as well. There are multiple layers of processing that go on in our visual system. You can't reduce it to three axes. The eye is not a camera, doesn't work like a camera, and can't be simplistically thought of as if it were a camera.

tbabb 9y ago
All of those things about visual processing are true. > You can't reduce it to three axes. This is my claim: It is possible to represent all possible visual stimulus with: f(direction, time) -> (a, b, c). That is what I mean by "vision is three dimensional". It is not possible to add another channel "d" to the (a,b,c) tuple which is not redundant; so anything you add would not be an extra axis or increase the dimensionality of the perception space. The brain/retina may generate lots of extra "channels" from processing this (moving) three-valued image, but those extra channels can't be stimulated independently of each other; they depend entirely on those original three degrees of freedom as a function of space and time. In that sense they aren't really "axes", because they aren't degrees of freedom. That's what I mean by "there isn't an extra channel." If you agree with that, then we don't disagree and we are just arguing semantics. :)
- edejong 9y ago
  It’s funny that you introduce time in your equation, because it shows how your view is incomplete. In our visual system, you cannot reduce to three dimensions without creating a recursive relation. It should be more like: Ret(a,b,c)_t = f(Ret(a,b,c)_{t-1}, current_stimulus) Since it is a recurrence, we cannot reduce to three dimensions.

roywiggins 9y ago

Don't forget purple, which doesn't exist in the rainbow. It's red and blue, which average to green but we see it as purple. Which validates the three-axis idea: purple is when the red and blue axes are dominant. But it's still peculiar.

mygo 9y ago
'red and blue' averages into green? Yeah, that's not really how our eyes perceive light. We see the colors that we see because certain wavelengths of light stimulate certain cones in our iris, which makes our brains hallucinate in color, basically. We see green when the short-wavelength-sensitive, medium-wavelength-sensitive, and long-wavelength-sensitive cones are all stimulated. A single wavelength of light around 520nm will stimulate all of these cones and satisfy the requirement for green to be seen. In fact this is usually the wavelength of light we'll find in a green laser. But there can be multiple different wavelengths of light in combination to make the eye perceive green as well. And that's what's happening when we see purple. When we see purple (magenta), we're never, ever, seeing just one wavelength. Because as we've said, there is no such thing as a magenta wavelength. It's not in the rainbow. So take red-wavelength light, and blue-wavelength light, with the key absence of green-wavelength light, and we'll see purple/magenta. But green-cone stimulating light must be absent or we will not see magenta. It's pretty interesting how what we see is not necessarily what's out there. Another interesting one is gray. There is no "gray" on the rainbow. Any time we're seeing gray, we're actually seeing a bunch of colors at once. Which is weird because gray appears colorless. But depending on the colors present that make us hallucinate that grey, there could be as few as 3 colors or even millions. We just don't see them because they're stimulating our cones in such a way as to neutralize each other. So under natural lighting, an aluminum macbook will be grey and colorless. But walk inside a room that only has red lighting (so no white lights) and that gray colorless macbook is now a colorful red. Anyways, what we perceive has never been a literal transcription of what's actually present. The brain takes in stimuli from the outside world, but it alone ultimately decides what we see. It shows us different things under different conditions. Different lighting conditions, under the influence of drugs, colors next to other colors, light arranged in certain textures, whether we're malnourished, whether we're daydreaming with our eyes wide open, whether we've just finished staring at an intensely bright light or a colored wall and are now looking at something else, all of it influences the colors that we actually end up seeing. The brain always has the final say in what we perceive, not the outside world. We're basically hallucinating 24/7, all the while thinking what we see is what actually is.