I’ve started seeing Sharp ads on TV, starring “Lieutenant Sulu in a white lab coat”, telling me they have invented a new TV that has 4 colors (Red, Green, Blue and Yellow) instead of the usual 3 (Red, Green, Blue), and that means colors can be more accurately represented.
Uh, really?
For the past 50 years we’ve had color TV’s that were based on the RGB standard, and I can’t recall anyone complaining about the color quality.
So what’s the deal? I know I need to run out and buy a 3D TV, but do I also need a 4 color TV? Or is this just unnecessary hype?
Hype that is (as usual) based somewhat upon reality.
The color model you choose (RGB, CMYK, etc.) determines a color space. There are certain colors that cannot be represented in any given color space. That’s why high-quality printing is often done with more than the basic four inks (cyan, magenta, yellow, black). You’ll see glossy gold ink, or bright red ink to punch up certain holes in the color space.
RGB certainly can display yellow, but the addition of pure yellow pixels broadens the color space. They algorithmically expand the broadcast colors to fill that space, and it does look somewhat richer.
I’d draw an analogy to high-end speaker systems. If I’m perfectly happy with my $200 speakers, why pop for more expensive ones? If you can tell the difference, and it enhances your experience, then go for it.
In fact, CMY should by itself be sufficient, but they add black too to make it more complete.
The biggest problem with the new Sharp TV is that the broadcast only contains three-channel information, so they have to extrapolate the yellow channel based on the three that they get. The question then becomes whether they can do a better job of extrapolation than your eyes could in the first place.
I have worked in Printing and CYM would not be enough by a long shot, hell in high end printing they use 6 colors. What about text? You just can’t overlay all the colors to get black like that it would look like crap and wouldn’t fit right. They didn’t add black to make it more complete they added black to get better tones and for TEXT.
You cannot make each color perfectly. For that we would use ink that was made to be that color, called a PMS, Pantone Management System. Sometimes we would do a light coat of metalic silver and print everything over that to have it flash out at ya, but you need black.
Or they may use their extra yellow in combination with one of the other three color emitters to better recreate what “standard” three color channel detectors measure.
Lets say you have a 3 color channel detector/imager. One of the channels is “blue”. It it sensitive to a wide spectral range of what you would consider “blue”.
However, your tv/emitter technology is rather limited. For some reason it can only emit a very narrow range of blue that isnt nearly as wide spectrally as what your detector was sensitive to. Then lets say you come up with another seperate emitter that that covers a different part of the “blue” spectrum, but still a part of the blue spectrum that was measured.
You use those TWO blue emitters in combination to better recreate what the blue channel measured. That would likely result in better color recreation than NOT doing it.
So, perhaps it is not really an extra channel that they are extrapolating for so much as an extra emitter to compensate for a spectral emitter/detector mismatch.
Perhaps, but I don’t think there’s a set standard (even a de facto one) for the spectral response function of the different channels of detectors, either.
Actually, they add black to account for the differential between theory and reality. Using real-world inks and paper, a combination of 100% cyan, magenta, and yellow yields a muddy dark brown, not black. There are perceptible differences between “pure black” (just the black ink) and “rich black” with the other three inks overprinted.
To elaborate on what ChrisBooth12 pointed out, text is another place where the real world of printing presses fails to live up to the beauty of the theory. When you’re trying to reproduce the fine lines of small text using three overlaid inks, it takes only a small misalignment to turn the text fuzzy and hard-to-read.