The Sony Alpha a7S III raises the bar for what a full-frame mirrorless camera is capable of. A revised 12.1MP Exmor R BSI CMOS sensor and updated BIONZ XR image processor offer faster performance, improved noise reduction, and a wider dynamic range, along with UHD 4K 120p video recording and internal 10-bit 4:2:2 sampling. The a7S III also does away with recording time limits and incorporates HLG for direct HDR production as well as S-Log2/S-Log3 gamma profiles for advanced HDR production with editing. 

Additionally, 5-axis SteadyShot INSIDE sensor-shift image stabilization is available, too, which minimizes the appearance of camera shake by up to 5.5 stops. The camera's menu system has also been updated for more intuitive navigation and the body design helps to promote better heat dissipation for improved continuous recording capabilities. Additionally, dual memory card slots both support working with CFexpress Type A or SD UHS-II memory cards for flexible and high-speed file storage. The updated sensor design also yields 2x faster readout speeds than previous generations and, when coupled with the revised BIONZ XR image processor, greatly reduces the rolling shutter by 3x and up to 8x faster processing and overall camera handling.

The sensor and processor combination also helps to achieve a wide dynamic range, of up to approximately 14 stops for stills and 15 stops for video, and 10 fps continuous shooting for up to 1000 uncompressed raw files for stills. Additionally, two codecs have also been developed: XAVC HS, which uses HEVC/H.265 encoding to retain more detail at smaller bitrates, and XAVC S-I, which is an intraframe codec for consistent performance and quality at bitrates up to 600 Mb/s.

Additionally, suiting long-form recording, the a7S III does not have any recording time limits to allow for unlimited clip lengths. The camera's physical design also features an improved heat-dissipating structure to promote longer possible recording times, up to an approximate 60-minute recording time at 4K60p. Also, users can use the same S-Log2 Gamma Curve that is found on high-end Sony Cinema cameras that squeezes up to 1300% more dynamic range into the video signal than traditional REC709, for increased post-production flexibility. HLG (Hybrid Log-Gamma) support is also available, along with the BT.2020 color space, for recording within a wide color gamut and, in addition to S-Log2, S-Log3 is also available for producing a 15+-stop dynamic range with increased grading control in the shadow to mid-tone regions of the image. 

This focusing system is available for use in all recording modes, to benefit both video and stills applications. Additionally, it is able to lock onto subjects quickly and can use Real-time Tracking for AI-based tracking on moving subjects or touch tracking for manual selection of the subject. Real-time Eye AF, suitable for both humans and animals, also ensures critical sharpness when shooting portraits.

Helping to fine-tune how the focusing system performs, seven-step AF transition speed and five-step AF subject shift sensitivity controls let you refine how quickly focus shifts from point to point and how smoothly focusing shifts occur. This allows users to confidently use any lens, even adapted lenses, for critical imaging without encountering blur from camera shake.