Re:Impossible colors
by sudont on Monday February 28, 2011 @05:07PM
(#2273183)
Back when I was a wee art student, I had a phenomenal printmaking professor who was an expert in inks. One of her projects was a monotype, and mine included a cloud background, but I couldn't get the colors right: a dusky yellow cloud background. You've probably seen the hue following an afternoon thunderstorm late spring.
I'd mix, and mix and end up with a dark yellow, that when printed over blue turned green, or reddish or some other stupid hue. And my printmaking professor came over, and she said to use gray, and some yellow, and some brown (please, don't ask for the exact ink mix). When we were done, the ink sat on the slab as a puce, but printed slightly yellow.
However, when printed over a thalo blue, it was exactly like I needed: yellow-blue. Not green, yellow-blue. It was the damnedest thing, and not lost on the other students: I had to remix it at least six times within a week for other people.
The color doesn't reproduce at all on screen, so I have to assume it's partially an optical illusion.
Re:Impossible colors
by jrockway on Monday February 28, 2011 @06:04PM
(#2273383)
The color doesn't reproduce at all on screen, so I have to assume it's partially an optical illusion.
I'm sure you know this, but RGB is not able to represent all possible colors, and monitors themselves are not able to represent all of RGB. This gives us a somewhat limited subset of available colors for use on screen, which is why (I assume) photographs don't look as colorful as the subject did real life. The film / CCD can't record all color information, and the print / monitor can't display it all.
Re:Impossible colors
by Someone on Tuesday March 01, 2011 @01:51AM
(#2274579)
Adding color channels can help. For example, Sharp sells LCD televisions with an extra yellow channel. Problem is that these need software computes/approximates/guesses at the perceived yellowness of pixels based on their RGB (for computer monitors) or HSV? (for television) values. I have no idea how well we know color perception to pull that of reliably, whether it actually can work across the population (including the colorblind), or whether they implemented the best-known solution.
Re:Impossible colors
by wtallis on Monday February 28, 2011 @08:44PM
(#2273852)
HDR (high dynamic range) displays are those that can reproduce wider differences between dark and light. What you're talking about would be called a wide gamut display, such as an LCD with RGB LED backlighting or a special wide-gamut fluorescent backlight.
Re:Impossible colors
by Natsu on Monday February 28, 2011 @05:05PM
(#2273173)
When I look at the blue/yellow thing on Wikipedia, I mostly get a headache. Depending on the angle I view it at, one color or the other dominates and it can change colors while I'm looking at it.
I don't seem to get a blue/yellow unless you count where I can get it to be yellow in the middle with some blue at the edges that tends to merge with the black border.
And I find that, hilariously, my visual system actively fights the merging of the boxes. When I successfully look at a real stereogram, there is a point at which my eyes snap into alignment and the stereogram pops out. In this case, it's like the opposite: I try to steer my eyes to the point where the blue and yellow boxes overlap, but if I get close they skitter apart. It's like trying to bring two identical magnetic poles together.
I'm sure this stuff is highly idiosyncratic. Everyone's visual system is different. It develops via visual feedback at early ages and so is different for everyone, sometimes to one's detriment:
Re:Impossible colors
by jodrellblank on Monday February 28, 2011 @07:02PM
(#2273565)
I don't get a single blue-yellow colour that I'm happy with, instead it either swaps from one to the other and back (patchily), or it holds semi steady as if I was looking at yellow through a blue mesh (or blue through a yellow mesh) but doesn't feel like a single colour, more like a checkerboard grid of two colours.
Re:Impossible colors
by JshWright on Monday February 28, 2011 @11:23PM
(#2274266)
So... does this blue circle go away eventually? Been a few minutes and I still can't look at a white surface without seeing a clearly defined blue circle...
Re:Impossible colors
by Someone on Tuesday March 01, 2011 @02:06AM
(#2274610)
Color is not a physical phenomenon, but a perceptual one; there are some wavelenghts that, in isolation, lead to perception of specific colors, but actually, there isn't a wavelength for any color.
Re:Impossible colors
by pak on Tuesday March 01, 2011 @12:09AM
(#2274369)
Right, although we have been trained otherwise by rainbow diagrams from birth, colors do not map 1:1 to wavelengths, and most of the light we observe is a mixture of wavelengths; we can only sample an intensity from each of three fuzzy bands of the spectra, and the rest is in our heads.
Re:Impossible colors
by waqf on Monday February 28, 2011 @06:48PM
(#2273526)
I once read that colour-blind synaesthetes (or color-blind synesthetes, for you furriners) were able to perceive colours through synaesthesia that they were physiologically incapable of perceiving with their eyes. Thus they abnormally associated concepts with normal colours that were abnormal to them.
Re:Impossible colors
by mitko on Monday February 28, 2011 @05:52PM
(#2273340)
They used to teach us elementary school that "blue+yellow=green". With the advance of science we fix some of our naive illusions. I don't know how many new we introduce...
I'd mix, and mix and end up with a dark yellow, that when printed over blue turned green, or reddish or some other stupid hue. And my printmaking professor came over, and she said to use gray, and some yellow, and some brown (please, don't ask for the exact ink mix). When we were done, the ink sat on the slab as a puce, but printed slightly yellow.
However, when printed over a thalo blue, it was exactly like I needed: yellow-blue. Not green, yellow-blue. It was the damnedest thing, and not lost on the other students: I had to remix it at least six times within a week for other people.
The color doesn't reproduce at all on screen, so I have to assume it's partially an optical illusion.
I'm sure you know this, but RGB is not able to represent all possible colors, and monitors themselves are not able to represent all of RGB. This gives us a somewhat limited subset of available colors for use on screen, which is why (I assume) photographs don't look as colorful as the subject did real life. The film / CCD can't record all color information, and the print / monitor can't display it all.
Indeed, but it’s not completely an issue of gamut: the hue is always off even if it’s balanced against a card.
I don't seem to get a blue/yellow unless you count where I can get it to be yellow in the middle with some blue at the edges that tends to merge with the black border.
I'm sure this stuff is highly idiosyncratic. Everyone's visual system is different. It develops via visual feedback at early ages and so is different for everyone, sometimes to one's detriment:
http://www.lazyeye.org/
You can see some imaginary colors here: http://www.skytopia.com/project/illusion/ipage-et.html
Also, any time I do these afterimage experiments I notice that my eyes are not very well aligned.
For example, one can have metameries (http://en.m.wikipedia.org/wiki/Metamerism_(color)), where different physiclaal signals lead to perception of the same color.