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Author Topic: Does an additional yellow gun add anything to TV images?  (Read 6075 times)

Offline nsbuk001

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Neil S. Briscoe  asked the Naked Scientists:
   
You will have seen the current adverts for a TV with an additional yellow colour gun.

Given you can produce any colour with the Red, Green, Blue guns, does the yellow gun really add any clarity?

Further, I can't remember if it was the same manufacturer, but I remember, when I was buying my first TV in 1982 - prior to obtaining my first computer - there was a TV then boasting the additional yellow gun.  Not sure that was a success or it wouldn't be being hailed as a new technology now, which it isn't.

Regards
Neil

What do you think?
« Last Edit: 19/06/2010 01:30:02 by _system »


 

Offline SeanB

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Does an additional yellow gun add anything to TV images?
« Reply #1 on: 19/06/2010 16:13:31 »
Consider that the broadcasters, the makers of DVD and Blu Ray et al  send a signal thay contains just information relating to just red, green and blue that makes up the picture on the screen. Yellow is a colour created by the eye combining adjacent pixels of red and green. Mixing in the set to illuminate the yellow and showing in addition to the output of the red and green makes for a really bright picture, but this is not what the original source wanted. This is like getting the TV in from the store, and turning the brightness, colour and contrast all the way up to max, like it was in the store, and then wondering why the pictures look so funny and without detail, and the room is so bright you get sore eyes just from watching for a minute.

 

Offline tommya300

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Does an additional yellow gun add anything to TV images?
« Reply #2 on: 20/06/2010 05:16:22 »
.
Well since the early 60s to the 90s there were only 3 guns that supplied the colors RGB!
There were never a 4th electron gun in the neck of the picture tube.

The early commercial LCDs were black characters on a painted background and was only used in a 7 segment display. As the technology advanced so did the LCD display evolved.
Cathode ray tube or should I say, picture tube technology is the thing of the past.
 
There has been attempts and marketed instruments to convert oscilloscopes cathoray tubes to digital LCD, which is still toyish looking displays and is not as refined yet. I know only first hand at least as far back as 2003.

 The Sharp Quadron claims that their LCD screen contains the yellow pixel added to the RGB raster. Remember it is digital technology now no more analog physical restrictions. This expands the spectrum of the color palate...
.
You still can go snow blind watching to much TV, computer operations, etc...
« Last Edit: 20/06/2010 05:21:03 by tommya300 »
 

Offline SeanB

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Does an additional yellow gun add anything to TV images?
« Reply #3 on: 20/06/2010 12:43:55 »
The extra gun cannot display more information than what is present in the input, whether digital or analogue. As all video is only going to be RGB in some form, the display being capable of displaying so much more is irrelevant. You are not going to faithfully reproduce colour if the display device is going to distort the signal, no matter how well intended that is.

Digital scopes though have benefited markedly from newer display technology, although at a price. You can now get a really light weight very capable instrument, with ultra high sampling rates ( over 1 giga samples per second on a non repetitive signal and a sample memory in gigabytes) with good voltage resolution that can display on a very high resolution colour LCD with some good built in measuring and storage abilities. Only drawback of them is the price, you can buy a car for less than some of these units.
 

Offline Bored chemist

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Does an additional yellow gun add anything to TV images?
« Reply #4 on: 20/06/2010 14:18:28 »
"This expands the spectrum of the color palate..."
No it doesn't. I can see exactly the same number of colours, no matter how they are presented.
 

Offline tommya300

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Does an additional yellow gun add anything to TV images?
« Reply #5 on: 20/06/2010 20:47:46 »
"This expands the spectrum of the color palate..."
No it doesn't. I can see exactly the same number of colours, no matter how they are presented.

What you mean is that we just can see just so much and that is the limit.
No matter the fact the machine presents the information, we just can not see it.

This is interesting.

Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four different types of cone cells in the eye. Organisms with tetrachromacy are called tetrachromats.

In tetrachromatic organisms, the sensory color space is four-dimensional, meaning that to match the sensory effect of arbitrarily chosen spectra of light within their visible spectrum requires mixtures of at least four different primary colors. As with the trichromacy normal in humans, the gamut of colors that can be made with these primaries will not cover all possible colors.

http://en.wikipedia.org/wiki/Tetrachromacy

 Industry support
The HDMI 1.3 specification defines a bit depths of 30 bits (1.073 billion colors), 36 bits (68.71 billion colors), and 48 bits (281.5 trillion colors).[2] In that regards, the NVIDIA Quadro graphics cards support 30-bit deep color [3] as do some models of the Radeon 5800 series such as the HD 5970[4][5]. The ATI FireGL V7350 graphics card supports 40-bit and 64-bit color.[6]

At WinHEC, 2008 Microsoft announced that color depths of 30-bit and 48-bit would be supported in Windows 7, along with the wide color gamut scRGB (which can be converted to xvYCC output).[7][8]

http://en.wikipedia.org/wiki/Color_depth

« Last Edit: 20/06/2010 20:56:17 by tommya300 »
 

Offline techmind

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Does an additional yellow gun add anything to TV images?
« Reply #6 on: 20/06/2010 21:35:05 »
I think you'll find the "Quattron" technology (as Sharp call it) -adding a fourth yellow pixel to the usual RGB- is primarily about improving energy-efficiency rather than improving colour gamut. As other people have said, gamut is limited by international standards and what is encoded in broadcasts/DVDs/Blu-ray etc.

To simplify the thinking slightly: if you consider a "white" backlight then each red/green/blue subpixel only passes 1/3rd of that energy even when fully turned on. Hence even full-white is never more than 33% efficient. However, you can add "white" (or Sharp's yellow) pixels with much less filtering so those pixels can transmit perhaps 60~90% of the backlight energy when fully on. This enables you to display bright (but relatively low-saturation) colours much more efficiently.
(Actually, because of polarisation losses, you lose another 50% in all LCD configurations anyway.)

The energy-saving approach is only relevant for LCDs where you're starting with a white backlight and filtering into RGB by subtractive (absorbative) filters. It wouldn't make much sense to try and do this for single-colour emissive displays eg CRTs. The LCD is quite hideously inefficient in terms of all the light lost/wasted - but unfortunately other systems which look better in principle tend to have poorer fundamental emission efficiencies, so the LCD is still the best-value solution at the moment.

The snag with the RGBY (or RGBW) approach is that you cannot reproduce saturated colours at as great a brightness (relative to white) as you could on a conventional RGB display... although bright/saturated colours are rarer in images in general so it can probably be fudged a bit.

This may be mostly an effiency thing, but the other use is to enable the display to show brighter highlights (like specular reflections on car bodywork, or the surface of water) more like a CRT television, making the images appear more vibrant and sparkly. I would guess that Sharp will do a mixture of both.

It's been talked about and tested especially for mobile (phone/handheld pda) displays for many years within the industry. It seems this is the first TV display where they've actually tried to market a product based on the principle.


A further trick you can do with RGBW or RGBY displays if you use "subpixel rendering" is an apparent increase in sharpness as the G and W/Y pixels are brightest and contribute most to perceived sharpness - and you get twice as many per triplet/quad. (The eye detects most sharpness in the green or luminance channel, and standard TV encoding, both digital and the old PAL/NTSC subsample the red and blue (or chrominance) channels at 1/2 to 1/4 the luminance resolution - as does typical JPEG encoding of photos...)

In fact, taking this a step further, if the aim is to maintain the same perceived resolution, you can have fewer (sub)pixels on your enitre display, which means you can have bigger pixels with less dead-space between them (making for a greater 'aperture') ... and again increasing total light throughput and efficiency.
« Last Edit: 20/06/2010 23:09:36 by techmind »
 

Offline Geezer

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Does an additional yellow gun add anything to TV images?
« Reply #7 on: 20/06/2010 22:13:31 »
Thanks Techmind. That's very illuminating - in more ways than one ;D
 

Offline Bored chemist

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Does an additional yellow gun add anything to TV images?
« Reply #8 on: 21/06/2010 07:01:01 »
"What you mean is that we just can see just so much and that is the limit.
No matter the fact the machine presents the information, we just can not see it."
No, I actually meant what I said.
 

Offline tommya300

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Does an additional yellow gun add anything to TV images?
« Reply #9 on: 21/06/2010 07:06:40 »
"What you mean is that we just can see just so much and that is the limit.
No matter the fact the machine presents the information, we just can not see it."
No, I actually meant what I said.
OK. Since I was refering to what the machine's added feature presented and not what you can see.
« Last Edit: 21/06/2010 07:13:46 by tommya300 »
 

Offline nsbuk001

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Does an additional yellow gun add anything to TV images?
« Reply #10 on: 21/06/2010 09:08:23 »
Thank you all - especially techmind - that has made things somewhat more clear regarding the provision of a fourth colour.

Regards
Neil
 

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Does an additional yellow gun add anything to TV images?
« Reply #10 on: 21/06/2010 09:08:23 »

 

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