Sigma has announced two new mirrorless cameras which will use its Foveon X3 image sensor (Quattro generation). The upcoming sd Quattro and sd Quattro H will employ APS-C and APS-H sized versions of the sensor respectively, and will also feature the Sigma SA mount, making them compatible with the firm's Global Vision lenses.

The new camera duo follow on from the SD1 Merrill DSLR and the more recent fixed-lens Sigma dp2 cameras, by using the Foveon X3 image sensor. This works differently to typical image sensors by using three layers of photodiodes each corresponding to a different RGB color, rather than the more traditional mosaic sensors. The result is said to be higher-quality images with rich color detail.

The Sigma sd Quattro will use an APS-C (23.5 × 15.5 mm) size sensor, while the sd Quattro H will use an APS-H (26.6 × 17.9 mm). Because of the way the stacked sensors work, calculating resolution is slightly different, but Sigma says the 19.6-megapixel top layer of the sd Quattro work with two five-megapixel layers below to offer the equivalent of 39 megapixels. Meanwhile, the 25.5-megapixel top layer of the sd Quattro H and its 7-megapixel middle and bottom layers, is claimed to enable it to give the equivalent of 51 megapixels.

Shared specifications of the cameras include use of the Sigma TRUE (Three-layer Responsive Ultimate Engine) III processor, and a 9-point autofocus system with phase difference detection and contrast detection. The cameras have an ISO range of 100 to 6400 and can shoot up to 14 RAW images with a top continuous shooting speed of 3.6 fps (frames per second).

The quirkily-styled cameras both measure 147 × 95.1 × 90.8 mm (5.79 x 3.74 x 3.57 in) which makes them similar to a mid-range DSLR, and offer equivalent access to manual controls. On the rear there's a 2,360k dot electronic viewfinder and a 3-inch 1,620k dot LCD screen. While there's no built-in Wi-Fi, the cameras are at least compatible with Eye-Fi SD cards.

Because the sd Quattro cameras use Sigma's SA lens mount, it means they will have access to the firm's Global Vision lenses in the Contemporary, Art and Sports lines. This includes increasingly well-regarded optics like the 18-35mm F1.8 DC HSM, and the newly announced 50-100mm F1.8 DC HSM Art.

There's currently no word on pricing or availability of the Sigma sd Quattro and sd Quattro H.

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