The Sony a7S is a compact hybrid still and video camera that, in many ways, puts video first. The extremely large full-frame 24 x 36mm sensor has relatively modest resolution of 12MP, which means when shooting UHD 4K video (with the 16:9 crop of the 3:2 aspect ratio sensor), the entire width of the sensor can be used without scaling or line-skipping, which has been for some time the Achilles heel of still cameras that shoot video. That large 12MP sensor also allows the a7S to shoot at ISOs as high as 409,600. The a7S also has many video-centric features: focus and exposure aids such as peaking, magnification, programmable Zebra levels, a histogram, and live audio levels can be displayed in both the electronic viewfinder and rear LCD screen. Plus, the a7S has extremely flexible picture profiles and gamma curves for video shooters, including S-Log2. The camera’s autofocus works in video mode, too, although the tracking is not smooth. The a7S uses Sony E-Mount lenses, but the shallow flange distance of E-Mount means it can be adapted with just about any lens that will cover a full-frame sensor, making it very flexible. The a7S can record 1080p video in 24, 30, and 60 fps as well as 120 fps in 720p, using Sony’s new 50 Mb/s XAVC S codec, which offers better performance than AVCHD―but it can shoot that, too, if you want. Audio-wise, the a7S has a headphone jack and 1/8" mic jack; XLR inputs can be added with the XLR-K1M adapter (SOXLRK1M), which interfaces with the camera digitally through the multi-interface shoe.
4K on the a7S
The a7S is unable to record 4K internally. Instead, it outputs uncompressed 8-bit 4:2:2 3840 x 2160 UHD 4K over HDMI at 24 or 30 fps for external recorders. The announced, but not yet available, Atomos Shogun (ATSG) looks to be the best solution for recording the 4K output in the future, as it’s light, relatively affordable, and can double as a monitor. Presently, recording that 4K HDMI output is a bit tricky, as most external 4K recorders use SDI. One portable option for recording the 4K output available now involves using two Blackmagic Design mini converters: the Blackmagic SDI to 4K (BLMCHS4K) is needed to convert the HDMI output of the a7S to 6G-SDI; then, the Blackmagic Mini Converter SDI Multiplex 4K (BLMCSDIMULT4) can convert the 6G-SDI signal to quad-link HD-SDI for use with the Ki-Pro Quad (AJKIPROQUAD) or any other recorder that can record quad-link SDI 4K. All of the items can be battery powered, but a pretty large rig would be required to make it work. Also, while not exactly portable, Blackmagic Hyperdeck Studio 2 (BLHYDKSP2) is also able to record directly from the HDMI output of the a7S.
- Entire full-frame image sensor is used when shooting in 4K
- Excellent in low-light situations
- Fully functional as a high-quality still camera
- Flexible lens mount can be adapted to work with virtually any full-frame lens