Not intended for all types of photography, but for studio, portrait and landscape shots. Foveon is a fantastic sensor in terms of detail and richness of color, but it requires you to work fairly calmly (“old-school”), with low sensitivity and a fairly limited dynamic range. However, the Super Fine mode on the body is extraordinary, coupled with the (slightly too slow, but excellent) Sigma Photo Pro software.
In short: for lovers of image quality that has nothing to envy medium-format cameras. The H version of the SD Quattro offers around 30% more surface area than an APSC, and generates images of around 60 MB in RAW (X3f and DNG). The “Super Fine” version is made up of 7 images, around 400 MB for RAW!
Great value for the money if you want MF quality for under 1000
It is not hi ISO camera most useful range is 100-400 but and this is a big but results are exquisite result of three layer sensor.
It is not the fastest but if you could l live with its limitations it is a great camera.
For more info just go to dpreview sigma forum.