FOVEON® X3TM and the Sigma SD9
Carver Mead, National Semiconductor and Synaptics jointly developed this new generation of CMOS technology that extracts each of the primary light colors (red, green and blue) from each pixel in the chip array by using layered technology.
Most cameras either use a mosaic filter mask that only gives one color to a given pixel. The arrangement of the mosaic may vary, some systems using equal alternating patterns (r-g-b, r-g-b, r-g-b), others using rows and alternating red and green or red and blue (proving 50% green, 25% red and 25% blue) or the Bayer pattern of irregular filters proving 60% green, 30% red and 10% blue.
Foveon technology is based on the well known Doppler shift of color or the rainbow spectrum, with red on one side, blue on the other and green in the middle. When light is refracted through the specially designed silicon CCD chip the color blue is filtered off at the top, followed by green and finally at the bottom is the red filtering layer.
Digital picture technology, just like our regular television technology (which dates back to 1950), is based on the fact that your eye and brain fuse color dots on the screen at a distance to “create” and image in full color. If you move up close to a color TV set you’ll see that these little dots are of varied intensity. A given intensity (or brightness) of a patch of many R-G-B color dots will fool your eye and brain into thinking it sees the color brown, yellow, red, pink or orange. If you look at the individual pixels of a color computer JPEG photograph, you’ll see that flesh tone and blonde hair is actually made up of green and red hues that, when viewed from a distance, seem to generate straw blonde hair or sun tanned flesh.
To help blend these various green and red hues (blue is used very little in both color TV and JPEG imaging as compared to green, which is the most prominent, and red) they blur the edges, which lowers sharpness. If you dial up “sharpness” or “contrast” on your digital camera or a piece of software like Adobe PhotoShop or Corel Photo Paint, the border lines of various colors are simply intensified, often adding deep green or red. These intensified border areas are often known as color artifacts.
Foveon technology is said to virtually remove all the blurred and artifact aberrations in a given picture and generate an image that is equivalent to 10 million pixels divided among each of the three primary colors. Actually the 3.5 megapixel F7 sensor chip only has about 3 million actual pixels, but each pixel is tapped for color at three layered locations.
Sigma is the first camera maker to experiment with this new technology in their SD9 digital SLR that compliments their already existing 35mm SLR line, thus current Sigma owners can use the lenses from their 35mm cameras on the digital body (which retails for $2,500, but is discounted by many vendors, including Ritz Camera who offers the Sigma SD9 body for just over $1,000).
Viewing is via a mirror and pentaprism or you can use a rear panel LCD screen. The Sigma SD9 has an automatic vertical metal focal plane shutter that goes from 1/6,000 to 15 seconds and synchronizes with electronic flash at a 1/180th of a second or less.
Power comes from 4 AA batters or two Lithium CRV3 packs, so you can use conventional batteries, including NiMH rechargeable in the AA size.
Above are two photos taken with the Sigma SD9.
Most 3.3 megapixel cameras split that matrix among the three color. Sometimes equally, sometimes favoring more green, so the image is formed by adjacent pixel readings for red, green and blue, with green getting almost 2 megapixels worth of coverage. The Sigma SD9 using the Foveon chip allocates 3.5 megapixels for each of these colors and stores them in a raw file format on to a low cost Compact Flash (CF) card. You turn this raw image files into either a TIFF or JPEG using special software that extracts the pictures directly from the storage card or via either USB or FireWire outputs.
If Foveon technology holds up and makes it into digital video camcorders we may see an ultra high quality HD camcorder that can deliver more pixels of R-G-B color (10 million) than even the best HDTV set will display (6 million dots). This could make home and semi-professional HD camcorders small, affordable and of a quality that rivals professional units costing over $25,000.
SD9 Digital SLR Camera Body - Exclusive Digital X-tra Package - FREE! + Free Memory Card Reader!
From our archives we have these articles from the 2002 Issues: