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Improving Digital Photography
Milican writes "'It's easy to have a complicated idea," Carver Mead used to tell his students at Caltech. "It's very, very hard to have a simple idea...And now one of Mead's simplest ideas--a digital camera should see color the way the human eye does--is poised to change everything about photography. Its first embodiment is a sensor - called the X3 - that produces images as good as or better than what can be achieved with film.'" We had a previous story about Foveon last February.
in Photography. Check out the article here.
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for an excellent (as usual) review of a camera based on this sensor check dpreview
http://www.dpreview.com/reviews/sigmasd9/
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"It's very, very hard to have a simple idea."
I don't know about anyone else, but this GW Bush bashing is getting a little tiresome.
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Before all of the replies saying that digital is for geeks and film will forever rule, please be sure that you have used current and professional quality digital gear, including 35mm gear made by Canon or Nikon with standard lens mounts, digital medium or digital large format backs (depending on the type of vs. film comparison you plan to make).
Consumer digital cameras are one thing... X3 is another (still hotly debated)... but most photo editors and labs out there right out agree that a Canon EOS-1D, EOS-D60, a Fuji S2 or a Nikon D1X or D100 is simply takes better pictures in nearly every regard (including resolution) than a 35mm film camera, with any brand or grade of film. With the latest range of full-frame cameras such as Canon's EOS-1Ds (11 megapixel, I believe) and Kodak's 14 megapixel offering, the distance between digital and film (with digital on top) will only increase.
And before you comment on other film sizes, realize also that many of the largest advertising companies shooting commercial spreads abandoned film long ago and are shooting with digital medium format or large format backs. Yes, many of the fashion or product spreads you see in your favorite checkout stand magazine are in fact digital these days.
Film is well on its way to becoming a playing for history hobbyists and an art tool for retro artists, and no amount of "ludditing" will change this.
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It sees a real "color" instead of on red/green/blue (dispersed in fine pixels of course). It may not be able to see red quite as well as other colors, but it only means that the sensitivity at the red level is the limitation you have for the picture as whole.
What you don't get is Moire patterns - at all!! That is what you probably hate when you say you hate "pixel noise" because it's totally obvious (due to the color changes), very distracting, and annoying to clean up after.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
How is this at all like the way the human eye sees?
This foveon system is like the human eye inasmuchas the light photons penetrate multiple layers and register at more than one levels in the same spot. For example, take a look at this cross section of the human retina.
Current CCDs only collect one waveband of light at one area. To simulate colour, they collect three different wavebands in adjacent areas on the surface of the CCD. Hence the funky moire patterns you that you see in tightly patterned cloth on the sample piccies on the site.
I hate pixel noise in my digital pictures. I have heard that since red color has to be detected at the deepest part of the silicon there is an abudance of noise in the reds.
If the upper layers are completely transparent in the red, then your concerns don't apply. As long as the actual transparency of the upper layers is reasonable, then there is little cause to worry - traditionally CCDs are far more sensitive to the red end of the spectrum than the blue so even modest photon loss at the red end is unlikely to seriously degrade the pictures.
The other nice thing about this technology is that the spatial size of the light bins is approximately three times larger than that for the equivalent physical sized CCD - that means better signal-to-noise ratios for this new technology.
Anyway, the presentations look compelling. I await cameras with reasonable numbers of megapixels (say 4Mpixels +) and reviews...
Cheers,
Toby Haynes
Anything I post is strictly my own thoughts and doesn't necessarily have anything to do with the opinions of IBM.
Current color CCDs only measure one of the primary colors at each pixel. Once a picture is taken, the missing colors are 'guessed' by looking at the surrounding pixels that did capture that color. This process is really slow because each pixel is missing 2 colors.
The X3 actaully measures RGB at each pixel, giving much better quality, at a higher speed.
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Great, now I can stop scanning in those 21Mpixel images from film, and get a 10Mpixel digital camera. Since it uses 3 layers, those pixels must count for more than twice as many from the 35mm film. And the dynamic range is surely greater tha slide film. Finally the shadow detail in that otherwise brightly lit scene that I needed to use slide film, and capture at 48bit can be resolved with a 24bit image! Now I won't need more memory - my files will be 1/4th the size, and look just as good!
And it sees just like we do! Same 3 colors, same intensity relations, all on each pixel! Because everyone knows the human eye has only one kind of sensor in it. It's not like mammal eyes that have rods and cones.
Sorry, film will be around a little longer....
- dave f.
Read a bit about The Color-Sensitive Cones
"In 1965 came experimental confirmation of a long expected result - there are three types of color-sensitive cones in the retina of the human eye, corresponding roughly to red, green, and blue sensitive detectors. "
"Follow your Bliss." -- Joseph Campbell
I hate to break it to y'all, but in the human eye, each spot in the fovea is occupied by one receptor, which is maximally sensitive at one wavelength -- in other words, it works the way that current digital cameras work. (Random Googled link.) I suppose that if the human eye needed to determine the color of a particular "pixel", it would have to interpolate, just like a CCD camera... but that's a moot point, because that doesn't actually happen in our visual system. (It's much, much more complicated than that.)
Now, this technology does sound like a great way to increase the resolution of digital cameras, if it's feasible. However, all this "neuromorphic" stuff is pure marketing. (Though I admit that "Foveon" is a clever name.)
MSK
t's pixelated still so you will still get Moire patterns as soon as the smallest details are finer than the resolving power of the X3 bins (think Nyquists theorem). However, the bizarre colours you get from a fine-grained black and white grid shouldn't be present to the same extent as all the measurements of colour intensity are done at the same point in the X3 layer, as opposed to the different spatial positions of the red green and blue bins in a colour CCD.
The bizzare colors (what I really hate about digital photos) are not just reduced - they are gone. If you read the review at DPReview.com you'll find that it has resolution right up to Nyquist is noise free and you get some detail beyond. Here's the relevant section (near the very end of the review, where they test against some resolution charts):
The SD9 is capable of delivering all nine individual lines of the horizontal or vertical resolution bars up to its maximum absolute resolution (sensor vertical pixel count) and slightly beyond. Note also that because the X3 sensor doesn't need a color filter array it doesn't suffer from color moiré.. Absolute resolution is just less than the Canon EOS-D60, Nikon D100 and Fujifilm S2 Pro (at 6 mp).
However, because the X3 sensor doesn't use a low pass (anti-alias) filter it is able to resolve detail all the way up to Nyquist. Beyond Nyquist the system will alias without any objectionable color moiré. Where a Bayer sensor camera would turn detail beyond Nyquist (such as distant grass texture) into a single plane of blurred color the SD9 will continue to reproduce some individual pixel detail (without color moiré).
"There is more worth loving than we have strength to love." - Brian Jay Stanley
As much as Foveon's well hyped and widely advertised (*cough*thanksslashdot*cough*) idea seems to make sense on the surface, their solution is far from perfect.
To sense an RGB (Red, Green, Blue) pixel one can use a veriety of methods. At the center of this technology lies the ability to turn a stream of photons into an electric current. This photodetector is colorblind, it is only capable of measuring the _amount_ of light, not it's color. To recognize color the estheblished method used to be to put several photodetectors near each other and put color filters in front of them. The most widely used color filter array is known as the Bayer pattern and consists of 2 green photodetectors (diagonal from each other) a blue and a red detector in a 2x2 grid. These 2x2 blocks are then repeated over and over to create the full image sensor.
Specialized software or hardware needs to take these individual Red, Green or Blue pixels and recreate a single RGB pixel, this technique is known as demosaicing. The major advantage of this method is the simplicity of the photodiode (photodetector). It allows for the creation of very dense image sensors that are now passing the 10MegaPixel barrier while keeping the cost down (start seeing 5MegaPix sensors for less then $100 before the end of this year).
Foveon's approach is to layer these color filters vertically.
The good:
- idealy you get R,G,B at each pixel.
The bad:
- very complex layered photodiode technology, this makes the pixels significantly bigger. Currently the pixels are bigger then a 2x2 bayer image pixel. The complexity also adds to the manifacturing cost, these chips will not be cheap for the forseable future.
- Color bleeding. For example: Photons in the green wavelenght do not nescecarily stop in the green layer, but might be picked up by the underlying red layer. This means that specialized hardware needs to apply a non-trivial color correction for each pixel layer.
Foveon's idea is a very interesting approach. Since they nicely pattented their idea shut, we will have to patiently wait for this single company to provide the world with this technology.
Side fact: The human eye see's colors using pigments that respond differently to different wavelengths. In the simplest model we can say that we see Red Green and Blue with spatially seperated pigments that resemble a bayer image sensor closer then the foveon's sensor.
High quality extremely expensive digital imaging devices are extremely good at capturing low amounts of light, but for consumer cameras the noise level in the electronics is too high so low light captures get faded out by the natural noise in the signal. Most CCD's used for astonomy are cooled through some means, usuall liquid nitrogen to bring the noise level in the sensor down to small fractions of what they would be at room temperature. This also leads into one of the negative points of the foveon tech which is that its noise floor is about 3 times higher than the cmos tech that Canon is using in their cameras like the D-30 and D-60.
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It's a neat technique to increase resolution, but the implication that the article gives that you need this technique to improve resolution is silly. Effectively each grouping of red, green, and blue sensing points in a CCD camera returns a single pixel. If you replace each red sensor with three smaller sensors (one red, one green, and one blue), you'll get the same increase in resolution. In theory you could lose data because a little bit of blue light hit the red sensor, but not the blue one, but in practice it isn't an issue. Assuming you can keep making the sensors small, you can keep scaling the resolution of CCD technology.
This is neat technology and may well improve the quality of cameras to come. But it's not essential to improving the quality of cameras.
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Primarily because it is still a bit buggy and bleeding edge. CCD is a proven technology, with a lot of time put in to its development. That is why Nikon has stuck with CCD chips. Canon has been using Bayer CMOS chips in some of their prosumer cameras, but the top of the line 1Ds still uses a CCD chip.
X3 still displays some odd behaviors under certain conditions, and until these problems are resolved, the "big guys" aren't going to want to put it into a high end camera -- especially when their customers have grown to expect a certain level of all-around quality and attention to detail from them.
V
I just finished reading the review at dpreview. (Thanks to all the people who posted the link). There may be a serious issue with this technology. In the review they mention "color clipping". Once one of the color channels reaches saturation, all color information is lost. This may be inherent in the X3 design.
The detector works by the difference in absorption of the colors of light. The first layer sees a lot of blue, with some green and red. The next layer sees a lot of green with some red and a little blue. The last layer sees a lot of red with only a little blue and green. What this means is that in order to determine the true colors of the reverse of this process needs to be calculated. However, if any of the detectors saturate (and the first is the most likely one), there probably is no accurate way to do this reversal. Currently, it looks like the camera makes these pixels grey, which looks aweful. They will need to come up with a better way of estimating the color of these pixels if this technology is to work well, and I have no idea if that's possible.
Note that a standard CCD with separate pixels can also have one of it's channels saturate. In this case, however, the pixel will simply become whiter than it should, which looks natural.