Sigma has unveiled the full details of its new SD Quattro H camera, which is due to be released in January 2017.
The key feature is set to be a newly developed APS-H size Foveon X3 sensor, which can produce 51-million-pixel images. For those unfamiliar with Foveon X3 sensors they offer three layers of stacked photo diodes. The top layer is sensitive to blue light, the middle green, whilst the bottom layer is sensitive to red. This means that full RGB information is available for each pixel, whereas on the common, single layer, Bayer pattern sensor 50% of photosites are green, 25% red and 25% blue, and for each pixel the colour value is calculated from the brightness of the surrounding red, green and blue pixels. Added to this the Sigma SD Quattro H uses 14-bit analog to digital converters, which, when combined with the Foveon sensor, should provide exceptional colour fidelity.
Sigma Foveon Quattro sensor layers
Previous Foveon sensors have produced exceptional detail and colour fidelity at low sensitivity settings, but have suffered as the ISO rating increases. The particular image quality created by Foveon sensors has made them a particular favourite amongst landscape photographers. As the new SD Quattro H uses a completely new Foveon sensor, it will be interesting to see how, and if, the image quality has improved beyond the first few sensitivity settings.
Resolution
The actual resolution of the top layer of the sensor is 6200 x 4152, whilst the middle and bottom layers are 3100 x 2076. This effectively means that the camera has 38.6-million-pixels, or photodiodes, but the actual resolution is restricted by the top layer, so in its APS-H mode the SD Quattro H will produce images with a 25.7-million-pixel resolution. However, thanks to clever interpolation, the SD Quattro H can produce a 3:2 ratio 51-million-pixel resolution image, which should, in theory, look as good as a 51-million-pixel image from a Bayer pattern sensor.
Lenses and Crop Modes
The SD Quattro H uses Sigma’s own SA mount lenses, and because of the use of an APS-H size sensor, it has a 1.3x equivalent field of view when using Sigma DG designation lenses, which are designed for full frame sensors. When Sigma DC lenses are used, the camera will automatically enter its DC crop mode, which has a 1.5x crop. It also possible to manually select the DC Crop mode when using DG lenses to take advantage of the in-camera 1.5x crop.
Body and Build
Externally the Sigma SD Quattro H uses the same, rather unconventional, body design as the standard SD Quattro. Strangeness aside, the body is made from magnesium alloy, which provides strength, whilst O-rings and dust seals, including around the lens mount, make the camera dust and splash proof.
Performance
There are few precise details on the AF system of the SD Quattro H, but what we do know is that it has both phase detection and contrast detection AF. Added to this the continuous AF mode uses Movement Prediction AF, which calculates the direction and the speed of subject movement to predict continuous focus adjustments. As you would expect, the camera also features Face Detection AF.
Up to 8 high resolution raw files can be captured when in continuous shooting mode, at a rate of 4.4fps. Switch to the Low resolution setting and this increased to 6.2fps for 16 images. With so many different modes available we will find out more about the continuous shooting modes when we test the camera in the coming weeks.
The Sigma SD Quattro H will cost £1,499 and will be available from January 2017
