Sigma's first DSLR — the SD9, Foveon X3 layered sensor, SA mount, OVF, no video, 2002.
The Sigma SD9 is a digital SLR announced in 2002 and Sigma's first DSLR, built around the Foveon X3 direct image sensor. It was notable as one of the earliest cameras to use Foveon's layered sensor design rather than a conventional Bayer colour-filter array, and it established the SA-mount SD line that Sigma continued for over a decade.
It is a digital SLR with an optical viewfinder and a moving reflex mirror, using the Sigma SA bayonet mount for Sigma SA lenses. Its Foveon X3 sensor captures red, green and blue at each pixel location through three stacked photodiode layers, rather than interpolating colour from neighbouring pixels. The body has no video and no in-body stabilisation, records raw files that require Sigma's Photo Pro software, and is APS-C-class in sensor size. It uses CompactFlash media.
The SD9 appeals to photographers drawn to the distinct output of the Foveon sensor, which many describe as delivering fine per-pixel detail and a particular colour rendering, best suited to deliberate landscape, portrait and studio work at base ISO. It is a slow, methodical camera by modern standards, with limited high-ISO performance, and rewards a patient, considered shooting style.
When buying used, note that early Foveon bodies operate slowly and can drain batteries quickly, so test power behaviour and carry spares. Check the shutter count where readable, inspect the sensor for dust and the optical finder and screen for haze or dead pixels, and confirm the CompactFlash and battery doors latch. Colour processing depends on Sigma Photo Pro, and service support for this early body is limited, so buy tested and factor in the workflow.