A chip off the old block
A REVIEW of a single piece of equipment might be considered of little value, given there is no comparison with a rival. But exception is made here for the SD9, which, thanks to its insides, is an exceptional camera. It uses a chip so revolutionary I contacted manufacturer Sigma months before the SD9 came to Hong Kong in the hope of being one of the first to sneak a look.
To appreciate what this camera can do you're going to have to take a step back. Remember primary school? Remember finger-painting class, when you wore a coverall made from your dad's old shirt? The teacher showed you that mixing yellow and red paint made orange, mixing red and blue made purple, and blue and yellow made green. By using three basic colours you could make just about any colour you wanted.
Light works in much the same way, but its three primary colours are red, green and blue. By mixing them, a computer monitor or television set can create almost any col-our imaginable. Video cameras, scanners and digital cameras do the same thing, but in reverse: they take colours and separate them into their basic red, green and blue components.
In a TV camera this 'unmixing' is achieved using a prism that splits light three ways, sending the reds to one imaging chip, greens to another and blues to a third. But digital cameras have only one chip, a handicap for which they compensate by using different pixels on the chip to capture different colours. The first sees reds, the next sees blues and the third sees greens. The camera then mixes the colours detected by the three pixels to create the final colour.
Here's where we find that the Sigma is a technical wonder. The fact that you need three pixels to create a colour from a standard chip creates all sorts of problems. But the SD9 uses a new chip called the Foveon X3, whose inventor realised light striking an imaging chip would penetrate its surface. How deep would depend on the light's wavelength. Shorter wavelengths, meaning red light, would penetrate furthest; longer wavelengths (blue) would not carry as far. All he had to do was place sensors at different depths within the silicon and hey presto! Every pixel sees all three colours.
The proof of the pudding though is in the eating - and the Foveon chip proves tasty: the differences between images shot with the SD9 and more expensive cameras from Nikon and Canon is obvious, with a solidity about the colour being a feature I would expect from expensive film. Foveon claims
its chip will increase the quality of digital photographs to the point where they will
be almost as good as film prints. I'm not sure it can capture the same range of colours or contrasts as film, but it is streets ahead of comparable technology. There are three problems with the $14,000 SD9, however. The first is the resolution, which at 3.5 megapixels lags behind that of point-and-shoot digital cameras. And as the resolution of chips increases, the problems the Foveon now eliminates will become less important. Second, the X3 chip is known for showing more digital noise than standard chips. At a speed of ASA 100 in bright light this was not a problem, but at ASA 400 the images were horribly noisy. Third, the Foveon is tragically stuck in a Sigma camera. Sigma is known more for its low prices than its high quality, and the SD9 shows the company's entry-level roots. It is cheaply made and the relatively poor quality of the 15-30mm lens I was given created problems bigger than those solved by the Foveon. Alas, unless Foveon can sell its chips to more main-stream companies, I fear the X3 will prove a promising bit of technology destined to wither on the vine. The Sigma SD9 is available from Mirama Camera, 25 Stanley Street, Central (tel: 2501-0918).
www.foveon.com The Foveon homepage gives you all the information about the X3 chip you can handle.
www.dpreview.com/news/0202/02021102foveonx3tech.asp Foveon has a well-illustrated explanation of exactly how the X3 chip works, but you must navigate through several pages.
www.sigma.com.hk/Main.htm Unsurprisingly, Sigma's Hong Kong website leads with information about the SD9. The site is in Chinese only, so for English information try the American site at www.sigma-photo.com.