Sigma's large-sensor mirrorless Foveon — the SD Quattro H, bigger X3 Quattro sensor, SA mount, EVF, 2017.
The Sigma SD Quattro H is a mirrorless camera announced and released around 2016 to 2017, part of Sigma's SA-mount line and a higher-format version of the SD Quattro built around a larger Foveon X3 Quattro direct image sensor. It sat above the standard SD Quattro in the range, offering a bigger sensor while keeping the same mirrorless body concept.
It is a mirrorless camera with no reflex mirror, using an electronic viewfinder and the Sigma SA bayonet mount for Sigma SA lenses. Its Foveon X3 Quattro sensor is larger than the standard model's APS-C chip, using three stacked layers that capture colour at each location rather than interpolating it. The body has no in-body stabilisation, records raw for Sigma Photo Pro, offers no meaningful video, and uses SD-type media in a weather-resistant shell.
The SD Quattro H suits landscape, portrait and studio photographers wanting the Foveon look on a larger sensor, with the electronic finder previewing exposure before capture. It performs best at low ISO and rewards a deliberate, tripod-based method, so it favours considered work over speed, consistent with the character of the Foveon line.
On the used market, expect slow operation and quicker battery drain than Bayer mirrorless bodies, so test power and carry spares. Check the shutter count where readable, inspect the exposed sensor for dust, and test the EVF and screen for dead pixels. Confirm the card and battery doors and weather seals, check the SA mount for wear, and note the reliance on Sigma Photo Pro and limited service support for the Foveon line.