Sharp Attempts To Re-Define What A Primary Color Is

Posted by: David Birch-Jones at 3:03 pm, August 18th, 2010

While the market release of the Sharp Quattron series flat panel HDTVs, which feature four sub-pixel colors as apposed to the usual three, the firm has embarked on an aggressive marketing campaign that includes snazzy TV spots featuring George Takei (of Mr. Sulu fame), all touting the advantages of watching HDTV with four “primary colors.” Indeed, the carton box the sets come in features a huge graphic with the four primary colors theme as the prominent message.

What they fail to mention is that in the TV world there are only three primary colors (red, green and blue). Yellow, cyan and magenta are secondary colors, and are each derived from the sum of a pair of primaries. Energize red and blue, you get magenta. Illuminate green and blue at the same time, you get cyan. Light up green and red, and you’ll see yellow as the result. Fire up all three, and white is what you get. The variable modulation of sub-pixel colors is how TVs display various color hues at various brightness levels.

It doesn’t help that when it comes to color printing, the roles are reversed, as that’s a subtractive process, as opposed to the world of color displays, which are emissive devices where the process is additive. With color printing, yellow is indeed a primary color, as is cyan and magenta, but that’s still no justification for obfuscation on the part of Sharp.

A few years back, Sharp had select LCD HDTV models that featured five color sub-pixels per cluster—two green, two red, and one blue. The earlier versions used only the three primary color sub-pixels at lower picture brightness levels, but around halfway up the scale, the two backup sub-pixels were slowly activated, such that at full picture brightness all five were emitting light at full toot.

To display white, the approximate ratio of color contribution is (and I’m rounding to the nearest decade here) green at 60%, red at 30% and blue at 10%. By having the extra pair of red and green sub-pixels, Sharp was able to increase color brightness at higher picture levels. By having additional yellow sub-pixels in the Quattron, they’re able to do pretty much the same thing (remember, yellow comes from combining green and red, which is why the Quattron isn’t quite as revolutionary as Sharp’s marketing message would indicate). After all, they’ve done this before.

By expanding the color gamut, a richer color palette is indeed possible, but there will be artifacts. In the case of the Quattron, the richer and more natural-looking color of grass that the set was able to reproduce, along with the more rich yellows, was offset by other colors that were over-emphasized, and this had a deleterious effect on the set’s ability to display natural-looking skin tones, with an unpleasant orange-y “fake tan” look dominating.

 

The diagram above shows the Quattron as measured at full brightness (100%). The triangle represents the color gamut of HDTV, and the six small squares (three at the corners, and the three along the sides) show the defined color points for the three primary and three secondary colors. Ideally, the six white dots should sit over the six squares. With the Quattron you can see that indeed the green and yellow dots sit well outside the triangle’s boundary—no doubt due to the fourth yellow sub-pixel being fully activated. The triangle sits within a much larger color gamut, which represents what humans are actually able to perceive.

 

This diagram shows the same measurement taken from the Samsung 3D plasma we recently reviewed. Note where the white dots are on the six triangle points for the Samsung, as compared to where they are on the Sharp chart. If I was to grade the Samsung, I’d give it a 99% score, especially since, and this is the big deal here, this level of accuracy comes right out-of-the-box at no extra charge, and with no calibration or extensive noodling of the set’s color management system, something a trained service rep or calibration technician can only do with expensive test equipment, software and expertise.

This difference in no small part explains why the Samsung got a TPV Recommended accolade from us, and the Sharp didn’t. In fact, I was sorry to see the Samsung go back to the manufacturer after testing was completed (I tried to hang on to it for as long as I could). The Quattron was back in its carton box within an hour after testing was completed.

‘Nuff said.

 

Comments

TD160 -- Thu, 08/26/2010 - 05:32

My BenQ w5000 (latest firmware) and most of the newer DLP projectors have red, green, blue, AND yellow, cyan & magenta primary colors wheel, its called BrilliantColor. I do not turn on the BrillantColor on my projector but the the projector still uses all the extra colors, for color realism, contrast & brightness the extra colors make a BIG difference ! 

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