Unveiled: Sigma sd Quattro Mirrorless Cameras and the EF-630 Flash

Bringing their innovative Foveon technology to the mirrorless market, Sigma is introducing the sd Quattro and sd Quattro H cameras—both of which see the inclusion of a direct image sensor as well as a unique form factor, compatibility with SA-mount lenses, and a range of distinct controls and handling features. Separating the two cameras is their sensor size, with the sd Quattro housing a 39MP-equivalent APS-C sensor, and the sd Quattro H housing a 51MP-equivalent APS-H sensor. Complementing Sigma's camera system is the EF-630 Flash, which features wireless TTL capabilities, 24-200mm zoom range, and compatibility with the optional Flash USB Dock.

sd Quattro and sd Quattro H

sd Quattro

Before delving into the camera specific assets, it's important to highlight what truly separates Sigma cameras from any other camera on the market—a Foveon direct image sensor. Unlike Bayer array sensors, which are found in the large majority of camera designs, that use a mosaic design across a single plane, Foveon sensors use a vertical 'stacked' design comprised of three layers of photodiodes within the silicon sensor, and each of these three layers corresponds to a different RGB color. With Bayer arrays, an RGB value is assigned to each pixel; with Foveon designs, each layer has a distinct RGB value, and each pixel can then record hue, chroma, and color values independently with no color interpolation. This results in rich color detail and smooth tonal transitions akin to how film looks and works, and also alleviates the need for an optical low-pass filter in order to also attain higher sharpness levels.

Taking this foundation one step further, these cameras feature Foveon X3 Quattro sensors that employ a vertical stacked design, but use a 1:1:4 ratio where the top blue layer is divided into quadrants (hence, Quattro). This enables a 30% increase in resolution compare to other Foveon iterations, as well as improved noise reduction and higher sensitivity. The APS-C sensor of the sd Quattro has a top layer resolution of 19.6MP, which equates to approximately 39MP when broken down into the number of individual photodiodes; and the APS-H sensor of the sd Quattro H has a top layer resolution of 25.5MP, which offers 51MP-equivalent resolution according to the total number of photodiodes. Additionally, for clarity, compared to full-frame image sensors, the Sigma APS-C sensor offers a 1.5x crop factor and the APS-H design is a bit larger, and offers a 1.3x crop factor.

Additionally, these cameras incorporate dual TRUE III image processors to complement the use of the direct image sensors. Three-layer Responsive Ultimate Engine, or TRUE, processors utilize Sigma's proprietary algorithm to decipher the unique data set created by the Foveon sensor and produce images with a distinctive pop. A sensitivity range from ISO 100-6400 is available for working in a range of lighting conditions, and the processor also affords a full-resolution continuous shooting rate of 3.6 fps for up to 14 consecutive raw files with the sd Quattro, or 3.8 fps for up to 10 frames with the sd Quattro H.

The processing capabilities and sensor design also afford a modest 9-point hybrid autofocus system, which utilizes phase-detection AF for speed and accuracy under difficult lighting, as well as contrast-detection for more refined accuracy when working in bright conditions. Both single and continuous AF modes can be used and Movement Prediction AF is available in continuous AF for tracking moving subjects. Face Detection AF can also be used for portraiture, and Free Movement AF lets you home in on fine details while acquiring sharp focus. Focus peaking can also be used for more controlled manual focus operation. Finally, its processing abilities facilitate a Super-Fine Detail exposure mode to reap the full benefits of the Foveon X3 Quattro sensor. By recording and compositing seven different exposures into a single frame, and saved as a unique X3I file, expanded dynamic range and detail can be recorded, which is especially well-suited for studio applications or other instances when shooting atop a tripod.

In addition to the unique sensor design used by Sigma, they are also well-known for the distinctive physical designs of their cameras, such as the recent series of dp Quattro compact cameras. The physical construction of the sd Quattro cameras is designed to offer a great deal of shooting stability and comfort, as well as intuitive handling while shooting. A high-resolution 2.36m-dot electronic viewfinder with 1.09x magnification is built into the right portion of the body, suiting right-eyed users. A rear 3.0" 1.62m-dot LCD monitor is also available. A dedicated switch can be used to manually select either of these viewing means during use, or an Auto selection is available for automatic switching between the two. Also unique to the design, a second rear LCD monitor, the sub-monitor, is placed adjacent to the main rear screen, and displays helpful shooting information at all times, including exposure settings and number of remaining frames on an SD card. Both LCD screens are covered by the same sheet of protective glass to lend a seamless appearance.

The sleek-yet-stable body also houses a Sigma SA lens mount, making both cameras immediately compatible with the array of SA-mount Sigma Global Vision lenses.

EF-630 Flash

In addition to the pair of camera announcements, Sigma has also released their newest external flash, the EF-630 Electronic Flash for Sigma, Canon, and Nikon cameras. An automatically-adjusting zoom range of 24-200mm supports use with a majority of focal lengths, and a built-in Wide Panel broadens the beam to cover focal lengths as wide as 17mm. Automatic and wireless TTL exposure control is possible, and a Slave Flash Function can be used for optical triggering of multiple flashes. Control over the flash's head is possible with -7° to +90° tilt, as well as +/- 180° swiveling, for bouncing the light off of a wall or ceiling for a softer appearance. FP Flash high-speed sync is also possible, for exceeding the typical flash sync speed of most cameras, and Rear-Curtain Sync fires the flash just before the shutter closes for creating blurred light trails of moving subjects. A modeling flash function is also available for previewing lighting setups while manual control lets you adjust flash power down to 1/128.

Not at a loss for incorporating something unique, Sigma has also enabled the ability to update the flash's firmware via the optional Flash USB Dock and Sigma Optimization Pro software.