Unveiled: Sony a7S Mirrorless Digital Camera
Released on the heels of the a7 and a7R mirrorless cameras, at the end of 2013, Sony has just announced the third model in this series: the a7S. Unlike the previous two models, the a7S, which stands for “Sensitivity,” is built with an entirely different kind of image-maker in mind. Right off the bat, the a7S's major selling points are a reduced resolution, yet still full-frame, 12.2MP CMOS sensor; the ability to record Ultra HD 4K (3840 x 2160) video with no pixel binning to an external recorder; and an expandable sensitivity range to ISO 409600.
At the core of the a7S is a newly-designed 12.2MP full-frame Exmor CMOS sensor, which works in conjunction with the same BIONZ X image processor found in the a7 and a7R cameras. The upgraded performance and enhanced technology found in the S model is capable of delivering an extended dynamic range, notably low image noise, and an extended sensitivity range of ISO 50-409600. Like the a7R, the a7S's sensor structure incorporates the unique on-chip gapless lens design to help increase light-gathering efficiency and promote greater image quality across the entirety of the sensor plane.
The combination of the processor and sensor also accentuates performance-related attributes throughout the camera system, including an apt 25-point contrast-detection AF system, which is sensitive to light levels as low as -4 EV; a top Speed Priority continuous shooting rate of 5 fps, as well as a 2.5 fps shooting rate with maintained autofocus; and support for an array of advanced video-recording capabilities.
Speaking of video capabilities, the a7S sees the most marked differences compared to its a7 counterparts with its ability to record 8-bit 4:2:2 UHD 3840 x 2160-resolution video to an optional external recorder via its micro HDMI output. For UHD video, the a7S utilizes a full pixel readout, eliminating any pixel-binning process. Beyond a noticeable difference in image quality alone, this technology also helps to lessen the chances of aliasing, false color artifacts, and moiré from occurring.
The a7S also gives you the option of recording HD resolutions internally to an SD memory card. Internally, 1080p recording has been boosted over the other a7 cameras by making use of the high-quality XAVC S format, with a data rate of 50Mbps. Video recording can be done using both the full-frame and cropped APS-C-sized regions of the image sensor, with the latter affording you the ability to record HD 720p video at a up to 120 fps for super slow-motion playback.
In an effort to improve on the professional video-recording capabilities of the a7S, support is available for the Sony’s S-Log2 Gamma setting, which expands the effective dynamic range by 1300% for increased detail in shadow and highlight regions. Dedicated picture profiles, such as black, level, gamma, and color adjustments, and a variety of markers, including zebra, can be employed for greater exposure control.
In regard to the physical structure of the a7S, it resembles that of the a7 and a7R: compact and sleek. It features the same 0.5" XGA OLED Tru-Finder EVF, with 2.36m-dot resolution, and the tilting 3.0" 921.6k-dot Xtra Fine LCD monitor. For extending the viewing and control capabilities of the camera, built-in Wi-Fi connectivity with NFC enables instant sharing and support for remote camera control from linked mobile devices.
In comparison to the a7 and a7R, the new a7S firmly holds its own and serves to further round out the broad-ranged abilities of the entire a7 series. While the a7R meets the high-resolution photographer's needs and the a7 sits as a versatile all-rounder, the a7S is poised to live up to its namesake in regard to Sensitivity. It is positioned to appeal to photographers and videographers who have a need to produce high-resolution video content as well as the ability to work in some of the most challenging of lighting conditions imaginable.