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Sigma & Foveon: A Hollywood Marriage?



The Digital Imaging Scene

Longtime readers of this column know its author to be an individual of splendid character, profound insight, and rapier wit. As true as that is, everyone knows what would happen if he married Angelina Jolie. His name would change. He'd become Mr. Angelina Jolie. Not because his sterling traits fell into disfavor, but because his missus was much more appealing. Your humble reporter would take the whole thing philosophically, of course, since the same thing happens to others. We could form a support group.

Maybe Sigma would sign-up. They're just entering the SLR digicam market with the SD9, a camera whose camera-like merits deserve examination. Indeed those merits are being widely examined, this camera having been photography's central legend for all of 2002. But it's like this. Me and the missus come to the door, and you get to choose which of us to look at. In just such a manner, the SD9, for all that recommends it, comes with a name-change of its own: Mr. Foveon Chip.

Photo by Don Sutherland Two of the three primaries were abundantly represented in this scene, and recorded with rich saturation. Clean, unsullied whites show that although the colors are strong, there is no "cast" to the SD9's color rendition

Think I'm kidding? Take a look at Time magazine from November 18, 2002. In a lengthy feature titled "Coolest Inventions of 2002," under the subhead "Pixel Perfect," one-third of the page is devoted to the invention of "Richard Merrill, Foveon." It describes how the invention works, and lists its availability as "December 2002." But readers couldn't buy a Foveon chip in December, nor can they today. They can buy only a Sigma SD9 containing the chip, and nowhere in the text is the camera mentioned. Want more info? Time says contact www.foveon.com.

True, there is a picture of the camera, uncaptioned and running a little smaller than the shot of the honeybee it presumably took, so maybe you'd guess you should contact www.sigmaphoto.com for details on "Mr. Foveon chip."

Chip Way Off the Old Block

The camera on its own is interesting alright. Just as interesting as others it could be compared with. But the chip is a first of a kind.

To an extent, it's a reinvention of digital photography. A reinvention that reverts to an earlier principle that the best picture comes when each ray of light strikes all three primary color receptors. That's how it works on film, where the color-sensitive receptors are placed in three layers of emulsion. It works because the layers themselves are translucent, permitting each ray to pass through and register on all. Until now, digital cameras couldn't do this. Instead, digicam pixels (using the Bayer pattern, et al) record one color each. Which color each records is determined by the color filter laid over it. If this one's red, the one to the left may be green, to the right, blue.

These one-color ponies are packed in quite tightly, millions in a space less than one-inch square, but a lightbeam is very small too. What if, for some reason, it connects up with just two of the adjacent colors, or only one? The picture starts looking weird. So manufacturers devised various filtering or algorithm routines to automatically correct the problems. Probably.

The Foveon Chip, whose name on the market is x3, found a way to stack the digital color receptors. It's not exactly like film, but it's in that directiona direction away from having to fix problems that the other chips themselves create.

Those fixes are all based on probablys. If the software sees that a large group of pixels are all one color, the one in the middle probably should match. It doesn't? Change it. Because it "probably" looks wrong because the camera diode "probably" didn't see the color it's supposed to. The camera's equipment, in turn, "probably" changes it correctly.

Photo by Don Sutherland Capt. Kosnac was backlighted here, causing a slight darkening of skin tones but overall, the results are quite acceptable, colorwise.

Controversy already swirls around the question of "how well" the Sigma camera works, fostered on websites from Europe and Asia. The SD9 evidently went on sale first there, and the reports are inconsistent. It's not always clear whether the cameras being described were actual production models, or beta works-in-progress. It can make a big difference.

Mr. and Mrs. Angelina Jolie worked together with PTN at photokina last September. We bumped into Mrs. Angelina crossing the tradeshow floor, who took us to the Sigma booth to meet Mr. Angelina. We had two hours, we were told, to have our way with our object of desire. Two hours was enough. The shooting conditions available were distressingly limited. Inside the Köln Messe, the light was a bit low for shooting at ISO 100 (we weren't sure the higher speeds were ready for testing). Outside was better, but not much. It was a gray, drizzly, foggy day, where tones were muted and edges softened. A picture out there could speak volumes about resolution, but not about color. There just wasn't much of it to speak of.

But Foveon's claims included superior sharpness. Their 3.3-megapixel chip, they said, produced pictures comparable to a conventional 7-or-so-megapixel CCD.

That's saying a mouthful. Not only because of the numbers, but also because the x3 is CMOS-based, not a CCD. Until very recently, it was widely assumed that CMOS imagers would not be as good as CCDs.

A drab day on the Rhine could have been a lucky break. Other reviews of SD9 prototypes worked in more broadly colored settings, and found fault with the yellows. A photography magazine said the yellow's too intense. A computer magazine said the yellow's too washed-out. The oranges, too. There wasn't much of either around our socked-in Cologne, so we had no side to take on the issue.

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