Sigma announced its SD1 SLR at the Photokina show. It's got a magnesium-alloy chassis. Sigma's earlier SLRs haven't fared well in the marketplace, but the company hopes the SD1 will do better in part through a larger and improved Foveon x3 image sensor. The new model, measuring 24x16mm, has a 15.3-megapixel resolution, but unlike the vast majority of cameras, each pixel captures red, green, and blue light, not just one of those three. The camera is due to go on sale in February.