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Kodak Unveils Brighter CMOS Color Filters
Posted by
Zonk
on Fri Jun 15, 2007 09:43 AM
from the seeing-you-in-all-the-old-familiar-places dept.
from the seeing-you-in-all-the-old-familiar-places dept.
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."
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Sacrifices color resolution: is it worth it? (Score:5, Insightful)
Re:Sacrifices color resolution: is it worth it? (Score:5, Informative)
Parent
Re:resolute colors required? (Score:4, Informative)
No... not really.
First of all, the Bayer pattern is...
RG
GB
Giving up one of the four sites to wide-band sensitivity as Kodak proposes, the same spatial pattern still has exactly the same sensitivity to red and blue; nothing has changed there. Red and blue sensor sites still alternate at the exact same spatial rate. But the new pattern has 1/2 the spatial (not intensity) sensitivity to green (which we are most sensitive to, remember); it has the same sensitivity to luma; and it probably has considerably enhanced sensitivity to infrared and ultraviolet, though that remains to be seen, and such an advantage is not as generally useful to most photographers (though those who enjoy IR and/or UV photography will love this thing if the sensor is truly wide-band.)
But there are complications; such as, Bayer filters tend to produce significant moire patterns, and the filters applied to prevent that reduce the available spatial resolution by as much as 1/2 along each axis anyway.
I've written numerous RAW image plugins for Bayer (and other) patterns, and believe me, it isn't as simple as 1/4 the color. This is a new configuration, and I've not written code for it as yet, but I would bet my boots that when the time comes to do so, the color resolution of an image will not suffer much, if at all. You'll still have RGB info available at about twice the moire filter rate. Spatial resolution shouldn't suffer either, because luma information is still available from the new arrangement. In terms of color images, what I'm trying to figure out is what the perceived advantage is.
Thinking outside the box of color images, though, I can imagine a simple 1/4 resolution B&W mode that can do infrared and ultraviolet with the proper blocking filters... that'd be trippy. :-)
Parent
Depends on the application (Score:2)
I expect this will have more value in cellphone cameras. Typically the noise floor goes up when the sensor shrinks, and increasing the brightness without increasing noise would be a massive boon for most cellphone photographers.
Probably not intended for SLRs (Score:3, Insightful)
Modern 'compact' digital cameras, however, which stuff 7-12 megapixels on 1/1.8" and 1/2.5" sensors (smaller than your fingernail) could benifit enormously from this. These sensors are already past the diffraction limit of most of the lenses, so a drop in color resolution may not be too damaging (the eye being less sensitive to color resolution, than luminance anyway). Kodak is claiming a 1-2
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This might make a nice second camera for the serious user, but most folks would be better off with the current technology.
Re:Sacrifices color resolution: is it worth it? (Score:5, Informative)
This additional intensity resolution is, of course, only at a quarter of that of the resolution a full bayer... but nobody ever said you had to discard the intensity measured by the red/green/blue filtered bits; in fact, you can't, or you can't very well determine color at all.
It's actually a pretty obvious setup (it has likenings to the RGBe storage format.. though that has much larger range, it also mostly separates color (RGB) and intensity (exponent)) - can't wait to see it patented - and makes me wonder why the Bayer pattern was the choice in the first place. I certainly know why they picked green as the go-to channel (human visual sensitivity, blabla), and why the there have to be groups of 4 in the first place (cells are square/rectangular.. design a triangular sensor cell, somebody - quick! gimme that hexagonal sensor).. but why just now Kodak pops this up..
Parent
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But the fact is that hundreds of millions of digital cameras have been made in an intensely competitive R
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Tim.
How about using that new non-reflecting material? (Score:4, Interesting)
Parent
Yes it is (Score:2)
The marketing hype surrounding resolution just keeps spinning further away from reality.
Digital photographic prints off the average production photo printer (my costco has them right on the floor) the lines per milimeter resolution is _way_ below what even a **really** good digital SLR with **great** optics can capture.
Also keep in mind the color gamut of the average digital camera is quite narrow, and unsophisticat
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'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.
To be honest, I wouldn't mind. If you buy a 10 megapixel camera that isn't a good quality SLR, you won't be getting much better quality than a 6 megapixel camera since the bottleneck for quality becomes the lens.
All it would really mean is that we absorb a delay in the relentless rise in pixel density for a dramatic improvement in colour depth.
This technology will sell, there's no doubt about it.
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Loss of color resolution is not that big a deal (Score:5, Informative)
Parent
The proof is in the pudding (Score:2)
we had 400 speed reversal film in the 50s (Score:4, Interesting)
I refer you to Tri-X b/w, and to Fujichrome 400 around 1972. a really nicely balanced and warm film. if you pushed it to 1200, you could peel the grains off the base and go bowling with them, but the picture held up remarkably well on the small screen. it was THE go-to magic film for 16mm newsfilm when it came out.
if that was a negative film, it would have been asa 800 with little more grain than the "fast" 125 color film of the time.
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Transparent AND absorbs light? (Score:3, Funny)
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Nothing too revolutionary (Score:2, Interesting)
CMOS version of Rods and cones (Score:5, Insightful)
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And I'll bet they've already filed a patent on it....
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Fixed that for you. : )
Re:CMOS version of Rods and cones (Score:4, Interesting)
The new Kodak filter pattern is still taking advantage of our better resolution for luminance, but is implementing it better by basing it on color filters (or the lack of them) that let more light through, thereby increasining signal-to-noise (especially needed in low-light conditions).
I'm not sure that this new filter pattern is optimal though. As another poster noted, R/G/B filters are too narrow and cut out a lot of light. You could still capture the color information with two broader filters more directly corresponding to the U & V of the YUV color space.
Parent
Sounds just like the new LCD display (Score:2)
why are sensors in RGB instead of CMY? (Score:3, Interesting)
They divide each sensor of the regular bayer pattern to 4, half white, half color. This way one can also report a 4-fold increase in the number of pixels, without really increasing the resolution. (which actually will be a boon for digital photography, since no one needs the current resolution anyway, because the optics doesn't keep up, but a megapixel race is on...)
But does anyone know why sensors use RGB and not CMY? a Cyan filter would let green and blue through, but keep red out, instead of blocking two parts of the visible spectrum for each pixel. This way, by simply switching color space, the camera becomes twice as sensitive to light. I.e. instead of use or something like that. One could even combine the two methods, and use white pixels, to gain a slight further increase in light sensitivity (from 8/12 to 10/12). Is there any reason that current cameras use RGB?
Re:why are sensors in RGB instead of CMY? (Score:5, Informative)
http://en.wikipedia.org/wiki/CYGM_filter [wikipedia.org]
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.
Parent
Re: (Score:3, Interesting)
But I don't understand why you don't have less noise. The wikipedia article mentions higher dynamic range. Isn't it true that twice as much light falls on each sensor, so you gain a stop, and because of that have less noise (because you need the shutter open for only half the time)? Or
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But does anyone know why sensors use RGB and not CMY? a Cyan filter would let green and blue through, but keep red out, instead of blocking two parts of the visible spectrum for each pixel. This way, by simply switching color space, the camera becomes twice as sensitive to light.
Let me just turn that around for you...
A Green filter would let cyan and and yellow through, but keep Magenta out, instead of blocking two parts of the visible spectrum for each pixel.
The color spaces are complimentary. Each
Re:why are sensors in RGB instead of CMY? (Score:5, Interesting)
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.)
Parent
I'd Rather Have Less Noise, Wider dMax (Score:3, Interesting)
For me, though, the problem is not so much speed as it is noise and dynamic range. That's because a lot of the time I still do fine-art level landscape and studio glamour photography -- neither of which are speed starved, but even the finest digitals could still use even less noise and wider dynamic ranges.
While DSLRs have a huge advantage over handhelds in this regard, it would still be nice to see improvements in s/n such that the darker zones maintained their clarity and detail. Even the finest Canon cameras suffer to a degree in this regard, at least for people with very high standards. Some of us have those standards because that is what our clients demand - and in some cases we still must use film to meet their criteria.
It's a virtual law that to obtain the best noise performance you need to use the lowest ISO speed that the camera can attain. So instead of bottoming out at 100, like most DSLRs, I'd like to see 25. Or better, 12.
For more info, visit http://www.normankoren.com/digital_tonality.html [normankoren.com]
Where is the transparent pixel? (Score:4, Interesting)
One of the problems with DLP projection TVs with a "color wheel" was that since every color lets only 1/3 of the light through, the picture was dim. So they added a fourth element "clear" that lets out all the light to get every projected pixel a blast of light they need and the remaining portions of the color wheel adds only additional brightness for each color.
This technology seems to be kind of similar. The transparent sub pixel detects over all lumninosity and the remaining pixels "adjust" for color. Very close to what we have in our retina too. Almost all our cylindrical cells respond only to luminosity and the cones respond, to varying degrees, three colors. A poster was complaining about losing "color resolution". I think millions of years of evolution has shown us the balance. You need about 90% of the pixels responding to luminosity and just 10% to color. The same ratio in our retina.
This Is Too Obvious (Score:2)
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Why not this pattern (Score:2, Interesting)
The patterns they suggested in the article were not as elegant as the Bayer filter (where each color formed an evenly spaced grid). They may be hiding the actual pattern for now or there may be some technical reason for those patterns that I don't understand, but I would suggest this pattern (C = Clear):
it keeps the same 4clear:2green:1red:1blue ratio but the different color pixels all form a regularly spaced grid.
Although I am old enough to remember the 80s.. (Score:2)
Is the clear array sensitive across the spectrum? (Score:2)
Does the clear array have a flat sensitivity level across the spectrum? Where it will give the same data value for the same number of photons striking it with a 700nm wavelength as it would for photons striking it that vibrate at 400nm?
If the sensor (for example here) was more sensitive to red, then this would skew the picture results significantly, especially if it picked up and added infrared light to the picture's data which isn't visible to the human eye.
Re:Is the clear array sensitive across the spectru (Score:2)
I imagine that's part of the reason it hasn't been done yet. Finding the "true luminosity" from a nearby Red, Green, Blue, and Clear CCD is probably nontrivial. I imagine that IR sensitivity isn't as troublesome as you'd suggest, though, since most cameras now come with IR filte
Other ideas for alternative color patterns (Score:5, Interesting)
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
Better than Foveon? (Score:3, Informative)
RG +BG arguments missing the point? (Score:4, Informative)
In printing technologies, at least in the early '90s they were using a technique called either "GCR" (gray color removal) or "UCR" (under color removal) which basically transfer almost all of the "light density" information from the cyan-magenta-yellow films of a color separation to the "K" film (black) -- because black ink is quite a bit cheaper than the alternatives. I have seen images printed with up to 90% of the density in the black that are virtually indistinguishable from images printed from a "normal" color separation by the naked eye, and sometimes if a high enough line screen value is used (+200 LPI) it is hard to tell that a print is a GCR'd image even with a magnifying glass.
So it stands to reason for me at least that if I devote more attention to capturing the "amount" of light with "one CCD eye" completely open, and the "quality" (hue and tint) of the light with my "other three CCD eyes" that are filtering for spectra, I should be able to do the same thing digitally that they have been doing optically in printing for yearsand still yield a superior result.
I'd love to hear a discussion about the best way to use the digital bits in a 32 bit "GCR" digital world by the way. For example, using 10 bits (1024 levels) for luma, 8 bits (256 hues and tints) for green, and 7 bits (128 hues and tints each) for red and blue, or whatever the optimal case could be
Thoughts?
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Cellphone cameras (Score:2)
DPReview has a good explanation (Score:2, Informative)
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The article says that sensors based on this will start to become available early next year, but I'd guess it may be a little longer until camera manufactures have tuned their on-camera image processing algorithms (and off-camera RAW algorithms) for the production sensors.
The larger format sensor cameras like the EOS 30D/350D (both are APS-C) don't suffer so much in low light anyway sinc