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."

Comments

Other ideas for alternative color patterns

[Thagg]

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

Re:why are sensors in RGB instead of CMY?

[MasterC]

This way, by simply switching color space, the camera becomes twice as sensitive to light. I.e. instead of ...

The issue is that the spectral density of sunlight is not flat. (I can't seem to find a good image for you.) Basically, it peaks at about 500 nm (yellowish-green) and tapers off toward infrared and ultraviolet. The Bayer filter has twice as many green pixels as red or blue, which reflects the sunlight power spectral density more than having one cyan, one magenta, one yellow, and one intensity would. In other words, sunlight is more green than red and blue.

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. :) Notice that of the three cone cells in our eyes, two heavily favor (534 & 564 nm) the yellow-green end of the spectrum. IMHO, the ideal colors for a camera filter would match the three peaks in our cones which decently lines up with the sunlight PSD.

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.)