Digital choices for photographers who own high-quality SLR lenses have been limited-namely, the $2,500 3-megapixel Canon D30 or a $5,000 pro camera. But this summer the field widens with three new digital SLRs. All will cost around $3,000. Canon's D60 and Nikon's D100 bring 6 megapixels within reach of the average snapper. But the dark horse is Sigma's 3-megapixel SD-9, which uses a Foveon X3 sensor to capture full color at each pixel-traditional sensors need four pixels for color. The trick: Each pixel has three light detectors instead of one; they're placed on the sensor's silicon at the precise depths that red, green, and blue light are absorbed. The result: The SD-9, with half the pixels, could surpass the D60 and D100 in image quality. We'll test the much-hyped Foveon cameras in future issues.