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Kodak Unveils Brighter CMOS Color Filters
brownsteve writes "Eastman Kodak Co. has unveiled what it says are 'next-generation color filter patterns' designed to more than double the light sensitivity of CMOS or CCD image sensors used in camera phones or digital still cameras. The new color filter system is a departure from the widely used standard Bayer pattern — an arrangement of red, green and blue pixels — also created by Kodak. While building on the Bayer pattern, the new technology adds a 'fourth pixel, which has no pigment on top,' said Michael DeLuca, market segment manager responsible for image sensor solutions at Eastman Kodak. Such 'transparent' pixels — sensitive to all visible wavelengths — are designed to absorb light. DeLuca claimed the invention is 'the next milestone' in digital photography, likening its significance to ISO 400 color film introduced in the mid-1980's."
Of course, you achieve this increased light sensitivity at the expense of losing 1/4 of your color resolution. Maybe if you want the increased sensitivity it might make more sense to pick up something like the Canon 1D Mk III, which, at least according to Ken Rockwell, gives great results all the way up to ISO 6400. I'd hate to lose 1/4 of my color resolution *all of the time* to get the added sensitivity that I only need for a small fraction of the shots I take.
Kodak has rediscovered what evolution found millions of years ago -- design a dual system such as the rods and cones of the biological eye. The average human eye has about 120 million sensitive, panchromatic rods and only 6 or 7 million color-sensitive cones (many in the central fovea). The brain merges the limited amounts of color information with the larger volume of B/W image data to paint color into the image that we think we see.
Two wrongs don't make a right, but three lefts do.
CMYK filters were actually tried:
http://en.wikipedia.org/wiki/CYGM_filter
They don't actually provide any practical benefit over RGB in terms of noise, if your final output is meant to be RGB, due to the mathematics of the color space transformation. And your final output is generally RGB, for digital photography; even if you print, the intermediate formats are generally RGB, and cheap consumer printers take input in RGB, not CMYK.
While I like Kodak's idea quite a bit, here are a couple of other ideas.
1) Sony was building cameras for a while with four color channels. There was the normal green, but also a different green they called "emerald" for one of the four Bayer pattern locations. Unfortunately, this was a solution in search of a problem, it never really caught on because there just wasn't any perceived benefit.
2) I do visual effects for films. For the last 50 years or so, people have been using bluescreen and greenscreen effects. The idea is to put a constant color background, and process the image so that any pixels of that color become transparent. Over the years, more and more lipstick has been applied to this pig -- so that you can now often extract shadows that fall on the greenscreen, pull transparent smoke from the greenscreen plate -- these things have become even more possible through digital processing.
Still, it sucks. Greenscreen photography forces so many compromises that I often recommend shooting without it and laboriously hand-rotoscoping the shots.
But -- say you had a fourth color filter, with a very narrow spectral band. Perhaps the yellow sodium color -- commercial lights that put out very narrow-band yellow are sometimes used for street lighting. If you had a very narrow-band sodium filter over 1/4 of the pixels, you could pull perfect mattes without 99% of the artifacts of traditional greenscreen and bluescreen photography. Finally (and this is killer!) you could make glasses that the director of photography and other lighting crew could wear that block just that frequency, so they could see the set as it really is -- without the sodium light pollution.
Still, Kudos to Kodak for thinking outside the box.
Thad Beier
I love Mondays. On a Monday, anything is possible.
It's done on TV all the time and nobody complains (chrominance is separated from luminance and often transmitted at much lower resolution). As has been pointed out below, your eyes are made up of rods (which see black and white) and cones (which see color), and only a fraction of those cones are devoted to each individual red, green, or blue spectrum. So your color resolution is already significantly lower than your luminance resolution. You can even see photos demonstrating this with a 9x decrease in color resolution (3x in each linear direction). You're most sensitive to green, which is why the Bayer sensors commonly used in digital cameras divide each 4 pixels into GRGB.
It is no coincidence (I suppose it's arguable if you call evolution a "theory" (with quotes)) that our eye is most sensitive to green light.
As a side note, the need for white balance on cameras is that spectral density for different light sources are not the same. Incandescents differ from fluorescents which differ from sunlight which is why incandescents have an orangeish tint and fluorescents have a blueish tint (that's where their frequencies have their peak power).
(The theory behind why chlorophyll is green (which means it reflects green and, thus, does not absorb the frequencies with the most power) are quiet interesting to boot.)
:wq