RGB to become RGBCMY

MPC: possibly the next standard? by r_glen · 2004-08-16 04:48 · Score: 5, Interesting

Does this mean I should hold off on buying an HDTV?

This will be great for Tetrachromats by Anonymous Coward · 2004-08-16 04:49 · Score: 5, Interesting

It's almost enough to make me wish I was a mutant mother of a color blind son.

Re:This will be great for Tetrachromats by QuantumRiff · 2004-08-16 05:32 · Score: 4, Interesting

That article explained alot. My GF asked me to hand her a her red shirt. I did.
She said, Thats ruby, i meant the red one.
So i handed her one of the other red ones.
No, thats rose,
On and on this goes, and then i finally tell her to pick the damn red shirt herself, she goes into the closet, takes a look at the 12 "red" shirts she has, and says, "see the red one, stupid". From what my buddies tell me, this is a very common issue, and perhaps these women have been overlooked for so long is that most of the doctors are men, and they just think the women are crazy. (My GF informs me that its really the other way around, we simple men are just blind!)

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What are we going to do tonight Brain?
Re:This will be great for Tetrachromats by jtriska · 2004-08-16 10:48 · Score: 2, Interesting

I think more than anything, that mostly proves your girlfriend is just better at placing color labels on parts of the spectrum.

When you train to be an artist, one of the first things you learn in color theory is to completely forget the names. They mean nothing, and theres a hundred different names by a 100 different paint companies for the same color!

Color for an artist is broken down to hue, temperature, saturation, and value.

The only names of colors that are important are the names of the primaries (which often in itself gets confusing as to whether your talking about the primary colors of light separated by a prism or the subjective primaries of pigment which when mixed together produce wildly different results depending on manufacturer)

Anyways, are women more sensitive to color than men? Maybe Tetrachromats, but normally, I'd say no. Perhaps more exposed to labels for whatever social reasoning though.

Isn't the CMY(K) color space smaller? by Anonymous Coward · 2004-08-16 04:49 · Score: 1, Interesting

If the CMY(K) color space is smaller than RGB, then why would it look more like cinema?

Biologically speaking, how... by Walt+Dismal · 2004-08-16 04:50 · Score: 3, Interesting

Certainly makes one wonder what happened to three-color retinas...

Re:Biologically speaking, how... by Anonymous Coward · 2004-08-16 04:56 · Score: 1, Interesting

The problem with three-color retinas is that the receptors for the three colors cannot be stimulated independently. See this diagram. There is no set of three wavelengths which can stimulate the red (green/blue) receptors without stimulating the other two.
Re:Biologically speaking, how... by Cecil · 2004-08-16 05:05 · Score: 4, Interesting

Yes, our eyes only have three types of cones, but unlike the color projected by a TV, they are not designed to respond to just one frequency of red, one of green, and one of blue. they have broad, overlapping response curves, each cone giving a different level of signal depending on the frequency of the light. The brain figures out the color based on the response of all three types of cones, not just the one that is active.

The stuff above is fact, the rest of this post is my pointless, unscientific, meandering hypothesis:

Obviously we use this concept with RGB signals to create colors like yellow, by tickling both the red and green cones at once with neighboring phosphors, but since the two colors are coming from very very slightly different places, the brain is not necessarily satisfied that it really is the color yellow. Basically, the more spectrum we can cover natively, the less chance there will be of someone's brain mumbling "that color doesn't seem... right"

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Random and weird software I've written.
Re:Biologically speaking, how... by osu-neko · 2004-08-16 05:05 · Score: 4, Interesting

Nothing. This just provides a better way to stimulate them. If one had the technology to vary the intensity of red, green, and blue over an infinite set of real values, then RGB would be able to perfectly replicate any color. In reality, the RGB color model used in displays today varies these values over a finite set of integers. One gets the best ability to reproduce colors that are red, green, or blue. Colors between these on the spectrum can be simulated by mixing these, thanks to the three types of cones we used to process color on the retina, but if in order to reproduce a particular color, we need 255 parts red to 41 parts green, we simply cannot increase the intensity of this color without distorting it (shifting towards green, because we've already maxed red). Thus, any RGB color model is going to more accurately and vibrantly display reds, greens, and blues, and simpler blends of these (where all values are equal, e.g. cyan), anything else is going to be limited in the range, grosser in steps between intensity, and less vibrant at the max. Adding pixels that display actual yellow (light of precisely that wavelength, rather than a blend of red and green wavelenght light exploiting the trick to stimulate our red and green cones to the same levels that actual yellow-wavelength light would), adding these pixels would increase the ability to accurately display these between colors, despite the fact that, in theory, only RGB is necessary. It's easier to add more between color pixels than to up the intensity range and lower the steps between intensities.

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"Convictions are more dangerous enemies of truth than lies."
Re:Biologically speaking, how... by iabervon · 2004-08-16 07:07 · Score: 3, Interesting

The human brain rarely says something isn't the right color. There's a huge amount of slop in the brain needed to produce the perception of stable colors of objects under different lighting conditions (if you light a room with light blue light, your eyes will adjust and report the usual colors of objects, even though the light reaching your eyes from them is obviously different).

The real issue is that, since the curves overlap, the green phosphor triggers the red cone to a certain extent, so green plus blue is cyan plus a bit of red, or a bit less cyan plus a bit of white. So the most pure cyan you can trigger in the eye with an RGB screen is less pure than the most pure cyan you get find in the real world. Purple is more of a mess (since the brain is actually making up colors for combinations that aren't generated by any pure wavelengths, and faking the idea that red is next to violet). But it all comes down to limits on the saturation of different colors due to not being able to keep from stimulating some cone or other.

Nice, but still shortsighted by krog · 2004-08-16 04:50 · Score: 5, Interesting

A truly revolutionary idea would be to include and project IR and UV in addition to RGB/CMY. Even though our eyes can't exactly 'see' IR and UV, they still form an important part of our realistic image perception. It's not unlike sounds above 20-25kHz in pitch; we don't 'hear' them, but our brain perceives them nonetheless and they are used for stereo imaging of a space.

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Cretin - a powerful and flexible CD reencoder

Re:Nice, but still shortsighted by baryon351 · 2004-08-16 04:57 · Score: 5, Interesting

Those sounds are also felt by other parts of our bodies than ears. I once rescued a small bat, and while it was recuperating, from time to time it would open its mouth and squeal its echolocating squeal. While I couldn't hear it, my partner and I could feel the noise in our chest & neck. I also spent some time videotaping the bat as it flew around the room ready to be released. Whenever it did its noise thing, the levels on the VCR shot way up high and all the other audio dropped out. Powerful stuff, and while it's still sound it was perceived in far different ways than just ears.
Re:Nice, but still shortsighted by pslam · 2004-08-16 05:03 · Score: 3, Interesting

It's not unlike sounds above 20-25kHz in pitch; we don't 'hear' them, but our brain perceives them nonetheless and they are used for stereo imaging of a space.
No, our brain does not perceive sounds much below 20Hz or above 25kHz, and our ears are physically incapable of receiving them in the first place, unless it's loud enough of course (in which case you feel it instead). I have never read any convincing evidence to the contrary in any paper that isn't written by either a vested interest, or by someone who clearly isn't in expert on the subject (usually those go hand in hand).
On the other hand, our eyes do perceive more than RGB. The rods have a slightly different spectrum response than cones, so you need a 4th primary probably centered around its maximum response to get closer to fooling human vision. You can see this effect for example on the leaves of trees at sunrise and sunset. A TV really is just a visual trick - it's emitting just enough of the spectrum to look like the real thing. If it makes your rods and cones respond in the same fashion as the real image would, it doesn't need to do any more. I'm unconvinced that adding 3 more primaries is really necessary.
Re:Nice, but still shortsighted by krog · 2004-08-16 05:09 · Score: 2, Interesting

It's not prohibitively expensive at all. There's nothing particularly special about IR or UV photodetectors. And the system would be backward-compatible with old cameras anyway -- the IR and UV channels just need to be zeroed.

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Cretin - a powerful and flexible CD reencoder
Re:Nice, but still shortsighted by Anonymous Coward · 2004-08-16 05:19 · Score: 1, Interesting

The CIE chromaticity diagram represents all colors which a non-mutant human being can see. It has a distinctly non-triangular shape. If you think you can recreate that gamut with only three base colors, I'd certainly like to hear how. Notice that RGB monitors show only a relatively small subset of the total perceivable color space.
Re:Nice, but still shortsighted by quantum+bit · 2004-08-16 06:28 · Score: 2, Interesting

I wonder how chickens perceive tv (assuming you let one in the house). Birds, fish, and turtles are believed to have far more superior color vision than humans. I would imagine they would see them as drab and colorless.

I don't know about chickens, but many birds (especially those that fly a lot / long distances) also have eyes with a quicker response time than ours. So they see more "frames-per-second" than humans are capable of perceiving, on the level of over 100 distinct images per second. I would imagine the constant flickering from the screen refresh would cause quite a headache. Flourescant lights would likely be annoying too.
Re:Nice, but still shortsighted by AmonRa1979 · 2004-08-16 06:35 · Score: 2, Interesting

You may not be able to hear pure tones outside of the 20Hz - 25kHz range, but you can hear several of these tones interfereing. It is one of the reasons certain audio formats try to record at sampling rates higher than 44kHz, which should be enough to accurately sample a 22kHz tone. While it is true that one wouldn't be able to hear an individual tone, it is not true that they are unable to experience a collective set of tones higher than 22kHz.

Of course the interference is simulating a frequency we can hear, but trying to record it with just the frequencies used for hearing will never accurately reproduce what your ear actually picks up. The same would go for playing it. In my experience (which isn't much) you end up with clicking noises when there are interfereing tones outside of the recording/playing frequency range that are interfereing to produce tones within the recording/playing frequency range.

However, this is slightly different than the topic at hand. Just using 3 colors of phosphors to try to cover the entire range just isn't enough. There are a lot of colors that this excludes. While the colors used in current televisions are enough to do a pretty good job, there is always room for improvement. The point is that the current phosphors used in TVs do not trick the rods and cones in your eyes well enough to produce every color visible by your eyes. Adding phosphors that produce intermediate colors will help improve color quality.

Since the majority of video capture is moving to digital (or so it seems to me), the next step would be to design CMOS sensors in cameras with the new 4-6 primary system (This is for digital still picture cameras, I'm assuming digital video cameras are the same). They now use RGB filters, and to accurately capture the colors, they would need to have RGBCMY filters with minimum color overlap.
Re:Nice, but still shortsighted by Kiryat+Malachi · 2004-08-16 08:24 · Score: 2, Interesting

Read up on psychoacoustics. Specifically, intertones.

Frequency A and Frequency B, played together, can cause us to hear an aphysical (not real) signal, (f1 + f2)/2. This is far more common with low frequencies. Thus, a 20-20k recording can miss signals that can create things we hear. Its not common, but it does happen.

There's neither such a thing as an intermediary color nor a primary; CMY are intermediary colors in the RGB vector space. RGB are intermediary colors in the CMY vector space. Since there's no physical reason to prefer either one, as each is simply a mapping of the space into 3 defined 'primary' wavelengths, you can't really claim either one as the preferred system. However, since RGB corresponds closer to the peaks in our eye's detectors, its become the traditional 'primary' system.

The correct way to look at the expansion is that, instead of the projection of a 3D space onto a 3D result, we will be taking the projection of a 4 (or 5, or 6)D space onto a 3D result. This means that, for a unitary (0-1 only) representation we can cover a wider range of the full result space.

RGB covers the entire result space, but only if you have the ability to use both positive and negative coefficients, and if you don't have limits on intensity. Given that we can't use negative coefficients in display systems (or positive in print systems), the additional vectors do expand the gamut.

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Mod me down, you fucking twits. Go ahead. I dare you.
(I read with sigs off.)

Colors or Pigments? by ryane67 · 2004-08-16 04:50 · Score: 2, Interesting

Last I knew there were colors (the actual spectrum of light) and then there were pigments of things (which actually reflect certain colors of the light)
so now they can project reflected colors, aka pigments? hmmm

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?SYNTAX ERROR IN LINE 42

Color Space by avalys · 2004-08-16 04:57 · Score: 2, Interesting

Can the human eye even distinguish between such fine variations in color? I know I've never found any flaws with images rendered in 24-bit color.

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Re:Color Space by DreadPiratePizz · 2004-08-16 05:17 · Score: 3, Interesting

This is true, but more colour depth is often needed in compositing work. It's not uncommon for a visual effects shot to be handled at 16 bits per channel, or twice the colour resolution of a 24 bit image. The reason is that it has a greater dynamic range. If you add two bright pixels together, the result will be white. But with more bits per channel, the pixels will be brighter than white, and still maintain values relative to other pixels, so that if you darken them later, no information is lost. Visually, 24 and 48 bit colour are indistinguishable.

Coming soon, a computer for TV! by ackthpt · 2004-08-16 04:59 · Score: 4, Interesting

Genoa partnered with Royal Philips Electronics NV, in Amsterdam, Netherlands, to implement the new color technology by modifying a family of rear-projection TV sets, which rely on liquid-crystal-on-silicon (LCOS) technology. In their current configuration, these sets produce images by shining red, green, and blue light from filtered white light onto a small microchip embedded with millions of tiny pixels made of liquid crystal that modulate and reflect the light to a lens system. This set of lenses amplifies the image and projects it on the screen, where red, green, and blue light overlap to form secondary colors.

Adding two extra colors to this kind of projection television has little impact on the price tag, says Simon Lewis, vice president of marketing at Genoa. He says the new Philips color-enhanced set, to be available next year, needs only a few additional filters and optical components to create the yellow and cyan light, with no changes to the more costly microprojection chip.

... The promised result of this multi-primary color (MPC) technology is a television picture that, with its truer, more vibrant color and brighter image, looks more like cinema than video.

Right. Right when we've got all these plants around the world cranking out inexpensive TV's using LEDS and LCD, some whizzo comes along and says, "Hey, look, a great idea and all you have to do is retool everything, develop some newer technology and keep selling it all at the same pricing you're currently at!"

Perhaps the main challenge in converting a video stream from a three- to a five-primary color system is doing it in real time, says Maureen C. Stone, ...

Yay, now we really will need a computer in every TV! More components - more to go wrong, more power consumption, etc.

"How the algorithm does that, precisely, is a secret well kept by Genoa. "It's part of their intellectual property," Stone says.

Yay, more intellectual property. This should drive prices down.

<curmudgeon>
Why, back in my day we didn't have remote controls and we had a folded playing card stuck beside the tuner knob to keep the picture from doing funny things, and we liked it!
</curmudgeon>

I'm sure it will look lovely, while watching older stuff from the bad old pre RGBCMY days.

"Gilligan!"

I'm like, totally there, dude!

--

A feeling of having made the same mistake before: Deja Foobar

Re:Yellow by mcbevin · 2004-08-16 05:00 · Score: 2, Interesting

Because green is one of the three primary colours of _light_, whereas yellow is one of the primary colours for like surfaces, which is a different proposition altogether. With light, yellow is gotten by combining two of the three primaries RGB (like red and green - I'm not 100% sure there), whereas green is a generally used as a primary colour thus nothing 'combines' to it.

You're thinking about combining paints (we all know from school art that blue + yellow = green). However they work in the opposite direction (the one is additive and the other subtractive). Thats why combining lots of paint colours gets brownish/black, while combining different coloured lights on the other hand moves towards white.

I know you're being sarcastic but . . . by bodrell · 2004-08-16 05:06 · Score: 3, Interesting

Far violet (~400nm) and far red (~700) are both visible. They might make the viewing experience much richer, and light at those wavelengths won't damage skin / eyes or cook your dinner.

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Si la vida me da palo, yo la voy a soportar Si la vida me da palo, yo la voy a espabilar

I've not seen this mentioned... by Glock27 · 2004-08-16 05:25 · Score: 2, Interesting

From the IEEE article:

What's certain, according to her, is that even though Genoa's technology increases the range of colors, it's not recovering the full original color information of a movie on film, lost in the conversion to other formats, like DVD. "It's kind of arbitrarily making images look better," she says, though people will in fact prefer the resulting colors, which will typically be more saturated and brighter.

Various video media may not have the necessary color resolution to drive these displays, but (given quality art assets;) newer video cards do.

I wonder how these types of displays compare to Iridigm's upcoming products on color fidelity. Those look quite interesting, especially at effective 200 DPI.

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Galileo: "The Earth revolves around the Sun!"
Score: -1 100% Flamebait

Why stick to the RGB standard at all? by Qzukk · 2004-08-16 05:27 · Score: 2, Interesting

Real advancement would be discovery of emitters that can match the XYZ Color standard. This standard was designed to mimic the actual operation of the eye, and therefore its gamut includes all possible human-observable colors.

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If I have been able to see further than others, it is because I bought a pair of binoculars.

Larger gamut.. *yawn* by Animaether · 2004-08-16 05:32 · Score: 4, Interesting

I'll wait for HDR display and feeds, thanks.

Judging from the gamut chart for this RGBCMY, the boost in color range is primarily in yellows and cyans. Gold, as they note, would be a good application. Cyan.. well, that's mostly skies - and those already appear just fine on TV. A fairly decent increase in magentas/purples as well (when taking the assymetric lobe into account), but again.. not seeing its application much.
Unless following the British royal family (lots of golds and purples) a lot, it doesn't appear to offer all that much. Especially considering movie people butcher things anyway (DVD gives a more stable picture, sure.. at the compromise of mpeg artifacting and even encoding issues.. twitches ever 25 frames are annoying - luckily only a few suffer from this).

On the other hand, a higher dynamic range would be immediately noticeable anywhere.
A sequence with the sun glaring into the camera ?
A car's headlights shining at the camera ?
Highlights on objects ?
Blown-out surfaces from bright lighting ?

All that could then more accurately be represented. And thanks to most things still being shot on film, or already on 10bit CCDs with, formally, underexposure but a gain for the operator, a good bit of extra range is already available in previous and current productions.
Whilst RGBCMY would only really be of use for film (as in, actual film) productions, as digital cameras are in much the same RGB limbo that current displays are.

Wide gamut displays by baxissimo · 2004-08-16 05:36 · Score: 4, Interesting

Wow, this is really cool.

There's a whole bunch of these wide gamut and high dynamic range displays suddenly.

At SIGGRAPH this year, there was a 6-primary (RGBCMY) projection system called IRODORI on display in emerging technologies:
http://www.siggraph.org/s2004/conference/etech/iro dori.php?=conference

There was also a high dynamic range display (capable of a greater range of brightness) from Sunnybrook Technologies at E-Tech:
http://www.siggraph.org/s2004/conference/etech/hig h.php?pageID=conference

And then I saw a few displays on the exhibition floor from NEC with a "WG" specifier for "Wide Gamut". NEC's WG monitor is still RGB but with purer R, G, and B phosphors to obtain a gammut wider than Adobe RGB.

And now there's this one. Way cool.

I can't wait till this becomes more widespread. The question becomes, what will the next color standard be for use in applications and APIs? It doesn't make sense to actually encode color as 6 values for display, since (most) humans only have three kinds of cones. It would make more sense to use something like CIEXYX for color interchange in that case. Especially if we're going to have this wierd mix of HDR and various wide gamut displays around for a while, each which has slightly different needs for color output. Best to just go with a neutral, well-defined intermediate colorspace.

IRODORI six-colorn display at SIGGRAPH by peter303 · 2004-08-16 05:42 · Score: 3, Interesting

Last week in the emerging technology section of SIGGRAPH a company or process called IRODORI was demoing a six-color projection system. (I could not find a reference on Google or www.siggraph.org.) When side-by-side with a conventional three-color you saw dramatic differences. Conventional is like looking at the world with wax-paper taped over your eyes. They claimed that conventional systems only covers about 55% of the CIE color chart, while they get over 90% color space. They bootstrap off of two conventional three-color projection systems. They put in different color filters and add special color separation software.

New standard still necessary by MunchMunch · 2004-08-16 05:47 · Score: 3, Interesting

From the article: "How the algorithm does that, precisely, is a secret well kept by Genoa. "It's part of their intellectual property," Stone says. What's certain, according to her, is that even though Genoa's technology increases the range of colors, it's not recovering the full original color information of a movie on film, lost in the conversion to other formats, like DVD. "It's kind of arbitrarily making images look better," she says, though people will in fact prefer the resulting colors, which will typically be more saturated and brighter.

And here's what you said: "This isn't a new standard, it's just an after effect applied to existing signals."

While you're right that it can be used in transitional technology, you're wrong that it's "just" an after effect. Nobody would say that Technicolorized B&W reproductions are the same as actual full-color originals. And here, you're going to need a format that preserves color information in the new 5 color system if you're going to exploit the real improvements in this color technology: closer reproductions of actual color.

Re:New standard still necessary by cmowire · 2004-08-16 06:04 · Score: 4, Interesting

It's probably simpler than you think.

CMY are really "combinations" of R G and B.

So, what's happening is that they are tossing in "intermediate" colors in roughly the same way as a 6 or 7 color printer. The exact equations are probably proprietary, but the process is pretty standard.

This comes in to play at two places. First, HDTV has a pretty ambitious color gamut, so videos designed around the HDTV gamut will look better, assuming of course that the source footage is equally high quality.

Second, there are colors that your eye can perceive that are not representable by the RGB system.

Overall, the research is already done. There's actually quite a few different ways to represent this data. PhotoCDs already use it. You want to use L*a*b or XYZ or one of the other CIE color systems.

I think it's interesting, but when I read the headline, my first thought was "Gee. What took them so long?"

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Gentoo Sucks
Re:New standard still necessary by Cuthalion · 2004-08-16 06:30 · Score: 5, Interesting

CMY are really "combinations" of R G and B.

This is false. C, Y, and M are different wavelengths of light from R, G, and B. Because the human eye only has receptors for R, G, and B, we can't distinguish between equal quantities of R and G and a single wavelength in between the two, namely Y. In other words, we are able to trick the eye into perceiving a full color spectrum using only three different wavelengths of light.

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Trees can't go dancing
So do them a big favor
Pretend dancing stinks!
Re:New standard still necessary by The+Snowman · 2004-08-16 10:47 · Score: 4, Interesting

I had never tried to think outside the RGB world because it 'technically' displays all colors, though it struck me that the colors in-between RGB will come out dimmer than they should.

No, RGB technically displays more discrete colors than our eye can see. That does not mean it "displays all colors." There are some colors RGB displays that we cannot distinguish between, and there are some colors we can distinguish that RGB cannot display.

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24 beers in a case, 24 hours in a day. Coincidence? I think not!

Re:Uses existing signal and price is right. by sweede · 2004-08-16 05:59 · Score: 2, Interesting

Cyan is not the opposite of red, it is the Blue - (minus) Red channel,
Magenta is Red - Green,
Yellow is Blue - Green,
Key (black) is Red-Green-Blue

you dont "mix" colors to get Cyan, or any of CMYK because CMYK is subtractive (RGB is additive).

You can say without fail that CMYK is the opposite of RGB though

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I follow the SDK and GDN principles.. Spelling Dont Kount, Grammer Dont Neither

Re:it won't matter much... by ScottGant · 2004-08-16 06:19 · Score: 2, Interesting

Actually, I would venture to say I know much more than you do.

I AM a graphic professional and I was taught before all this reliance on calibrations and color models and the like. We color correct images using actual CMYK data that we read from the image itself. Just because a monitor is calibrated to a given image-setter or "direct-to-plate" doesn't mean anything if you don't know the basics.

I'm talking about printing and the printing industry that has totally fallen in love with Colorsync and it's ilk. Yes, it doesn't take a brainiac (as you've proven with your post) to work with color anymore.

I know, I'm fighting a losing battle and the shift from pre-press houses to induviduals with calibrated monitors and ink-jets has totally changed everything. But it's nice to go know the roots.

If you really knew what you were doing there Tumbleweed, you could color correct an image using a gray-scale monitor! But then again, why?

Some advice: when you don't know what your talking about, shut the fuck up.

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"Music is everybody's possession. It's only publishers who think that people own it." - John Lennon.

True cyan by Twinbee · 2004-08-16 06:34 · Score: 2, Interesting

I'm glad to see they're upgrading the colour on displays, as I've always hated the weak saturation of the cyan/green colour in particular (much closer than you'd think to pale grey than actual cyan).

For those that want to cyan should look, try the 'Eclipse of Mars' illusion at this site.

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Why OpalCalc is the best Windows calc

Re:Yellow by dasmegabyte · 2004-08-16 06:42 · Score: 2, Interesting

Green is not one of the three "primary" colours of light. Light doesn't have primary anything -- it's a bunch of waves oscilating at different speeds. It's the human eye that has "primary" receptor that detect ranges of color, ranges that roughly approximate blue, red and green. Real yellow is not a combination of a red wave and a green wave of different intensities...it's a discrete yellow wave with its own intensity.

It doesn't make that much of a difference, overall. But since everybody's perceptions of RGB percentages are different, everybody's ideal color matching values in an RGB plane are different -- meaning there's no way to accurately reproduce a particular color in RGB.

RGBCMY is a start...but the ideal would be an emitter that released the exactly correct waveform of light at a pixel. It's not too difficult to perceive a color system that used a floating point wavelength value, an intensity value, and maybe a direction to display an image produced by a series of photon emitters...

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Hey freaks: now you're ju

Re:it won't matter much... by Tumbleweed · 2004-08-16 06:47 · Score: 2, Interesting

You're talking about a limited application of graphic design. If you're designing something from scratch, you need to have your equipment colour calibrated FIRST. If you're trying to match something else, then yeah, you can work around it. If you want your print output to match your display output you'd best get that equipment calibrated, no matter what you're doing.

Go caving sometime by freeweed · 2004-08-16 09:30 · Score: 3, Interesting

There's a huge amount of slop in the brain needed to produce the perception of stable colors of objects under different lighting conditions

Boy, you can say that again. For anyone who *really* wants to experience this, I suggest you go caving some time. In a deep enough cave that no outside light penetrates. Last weekend myself and a group were out, and we all had different models of headlamps. Now, the cave we were in has 3 interesting things going for it here: very banded & multicoloured rock, lots of ice (again somewhat multicoloured due to how it forms over the centuries), and human artifacts (a fair bit of paint on the walls, general human refuse, etc).

Here's the trick: you're in an area where your eyes have never seen the surroundings in natural light. Effectively, you have no reference point to know what colour things are. Now, I personally have one of the newer LED/incandescent combo headlamps (an amazing combination by the way, and for those with any doubt, 3 white LEDs will provide more than enough light for at least 20' around you - no more trying to focus right in front of your feet :). Alternating between the LEDs (white light) and the bulb (yellow light) was... interesting. My eyes couldn't decide what colour things were. Relatively speaking, sure. But I'd go for a while with just the LEDs, my eyes got used to that, then switch to the bulb. Suddenly, switch to the bulb, and everything gets weird. Even subtle things like depth cues get messed up, because your brain is frantically trying to re-colour what you're looking at.

This really didn't happen with things like our clothing or other gear, because my brain "knew" what colour that stuff was, having seen it outside, and it adjusted easily. But the rocks, ice, and *especially* the tagging on the walls - very creepy effect. Things that looked green in one light could be red in another. The ice was fun, because it's actually somewhat brown/yellowish in some layers (dirt, I suspect). But the brain wants to colour it blue-white.

We also had a good game of "guess my eye colour" - many of these people didn't know each other very well. I think we scored less than 50% overall :)

--
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.

Impossible by r6144 · 2004-08-16 17:26 · Score: 2, Interesting

Any physically existing color (i.e. it is the response of the human eye to a light signal with a certain frequency spectrum) is in the horseshoe-shaped area in the CIE chromaticity diagram. The X, Y and Z base colors are not inside that area, thus they are impossible to produce physically using any means (unless you are going to connect the vision-related part of the brain to something other than a normal eye...).

Indeed, with a number of primary colors (which must lie in the horseshoe shape), one can only produce the colors lying in their convex closure, which is the smallest polygon containing all the points corresponding to the primary colors. Since the horseshoe shape is not a polygon, it is impossible to produce all human-observable colors by mixing a finite number of primary colors.

sRGB can't describe all the colours we can see by Saville · 2004-08-16 17:34 · Score: 2, Interesting

I couldn't see this info elsewhere. I was at a colour course at Siggraph 2004 last Sunday for most of the day (8:30am to 5:30pm on just colour!). I also got to see both the IRODORI wide gamut display and the HDR display, both were very cool. Once we get HDTV it is clear we can go at least one more step.

The problem with RGB is it can't describe all colours the eye can see. This was a problem for the guys that made Salem Cigarettes. The problem is their brand's colour lies outside of the small RGB gamut! The best they can display for their brand in RGB is only an approximization. Sure it is a blue-ish green-ish colour when you see it on TV, but it isn't what you would actually see in reality or with a wide gamut colour device. They weren't the only company with this problem.

This is a huge problem for hundreds of thousands of people every day. There are colours that exist that they can't see in their work. They can sit down on a computer and work in an alternative colour space such as L*a*b* and create these colours and even print these colours, but thanks to our RGB monitors they can't view them! What do they do when they have to print an add for Salem Cigarettes? Guess and check I suppose...

Technically RGB can represent more colours than we give it credit for, you just have to allow for negative values which is only useful mathematically until we invent anti-photons to remove light...

Here is a short link to make explain details:
http://www.cs.sfu.ca/CourseCentral/365/l i/material /notes/Chap3/Chap3.3/Chap3.3.html

A few more things I'll add from that course; HVS is basically the worst colour space and CIELAB or L*a*b* is the best. CYMK is technically multiplicitive, not subtractive like so many people like to call it. Our eyes are sensitive to short, medium, and long wavelengths, not Red/Green/Blue. RGB happens to mostly match up with what we percive, but it is an over simplification.

For the real keeners here is a nice FAQ about this:
http://www.poynton.com/notes/colour_and_gam ma/Colo rFAQ.html

Re:Bandwidth by SLi · 2004-08-16 18:21 · Score: 2, Interesting

We have to separate the two very different sources of loss here:

1. Loss due to the target color space not being able to represent the color in the source color space; for example RGB cannot represent all colors visible to the human eye (without having negative components);

2. Precision loss in the conversion.

Now these two are very different beasts, and #2 can be avoided to an arbitratry precision if you for some reason wanted to. Actually with some cleverness the conversion could be avoided altogether until the XYZ signal is in the viewing device where it can be converted to the nearest matching color you can display to an arbitrary precision (unless of course it's an XYZ display in which case you don't need to convert at all :-). On the other hand, the RGB color space is fundamentally not able to represent all colors visible to the human eye with positive amounts of R, G and B - this is #1 type loss.

Now, to your actual claim:

While the shade of color reproduced with such a conversion might be close, it won't get the color back all of the way and will lose some information, and information that will be noticed by a good eye.

Ah, but you forget that human eyes are actually discrete too. There's a limited number of receptors for each "primary color", and the intensity of that component as interpreted by the brain is determined by (number of receptors activated)/(total number of receptors). Thus with enough precision, it is possible to convert even with discrete signals from a more restrictive color space to a less restrictive one without any loss you could perceive.

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