Sigma's flagship Foveon DSLR — the SD1, higher-res X3 sensor, SA mount, OVF, no video, 2011.
The Sigma SD1 is a digital SLR announced in 2011, the flagship of Sigma's SA-mount SD line and built around a higher-resolution Foveon X3 direct image sensor. It marked a major step up in pixel count for the SD series and launched initially at a high price before Sigma reworked its positioning with the closely related SD1 Merrill.
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 APS-C-class Foveon X3 sensor captures red, green and blue at each location through three stacked layers instead of interpolating colour, yielding fine per-pixel detail. The body has no in-body stabilisation and no meaningful video, records raw for Sigma Photo Pro, and uses CompactFlash media in a weather-resistant magnesium-alloy shell.
The SD1 suits landscape, portrait and studio photographers who want the Foveon rendering at higher resolution, working deliberately at low ISO where the sensor performs best. It is a slower, more specialised tool than mainstream DSLRs, with limited high-ISO reach, and it rewards careful technique and a considered pace.
When buying used, expect the slow operation and heavier battery drain typical of Foveon bodies, so test power and bring spares. Check the shutter count where readable, inspect the sensor for dust and the finder and screen for haze or dead pixels, and confirm the CF and battery doors and weather seals. Processing depends on Sigma Photo Pro, and service for the line is limited, so buy tested and account for the workflow.