Slashdot Mirror
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.
Random is the New Order.
for an excellent (as usual) review of a camera based on this sensor check dpreview
http://www.dpreview.com/reviews/sigmasd9/
-- the cake is a lie
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.
Remember, I said "please be sure you have used the gear".
The ISO 1600 and 3200 shots from the pro digitals are easily less grainy and have better dynamic range than their film counterparts. Try it. And my EOS-1D can do 1/16,000 shutter speed with zero lag. Is that fast enough for you?
Yet another person who is bashing without trying.
STOP . AMERICA . NOW
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.
(appended to the end of comments you post, 120 chars)
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.
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