The Sigma sd Quattro is the first mirrorless interchangeable lens camera released to feature a Foveon X3 Direct Image Sensor. Matching the APS-C format Quattro sensor first seen in the dp Quattro line with a mount that accepts all Sigma SA-mount lenses in the Art, Sports and Contemporary line (along with many older Sigma lenses) is a potent pairing for photographers who demand the utmost in image purity combined with the flexibility to pair the camera with a wide range of Sigma interchangeable lenses.