The Sony Alpha 7S III comes with the new Bionz XR image processor and a 12.1-megapixel back-illuminated full-frame Exmor R CMOS image sensor. The ISO range has also been improved a bit on the Alpha 7S III now going from 40 to 409,600 instead of the 50 to 409,600 range on the Alpha 7S II. The Mark III can now record 4K video at 120p with 10-bit 4:2:2 colour depth. It also brings 4K 60p 16-bit RAW video HDMI output capability, which Sony says is the first time in the Alpha series. This full-frame camera can take still images at up to 10fps more than 1,000 consecutive uncompressed RAW images.

The Sony a7S Mark III uses the newly launched CFExpress Type A memory cards and supports two of them. The company says data transfer speeds on these CFExpress Type cards is 1.7 times faster than that of SD cards. They have advertised 700MBps write and 800MBps read speeds and come in 80GB and 160GB capacity.

The Sony Alpha 7S III uses a Fast Hybrid auto-focus (AF) feature that combines phase-detection and contrast-detection allowing the camera to track subjects faster over a wide area. It has 759 point phase-detection AF sensors that cover 92 percent of the image sensor. The Alpha 7S III features 5-axis optical in-body image stabilisation with an additional Active Mode for more advanced handheld movie shooting. Sony says this camera's 9.44 million-dot OLED electronic viewfinder is the brightest and largest in the world. The menu system on the full-frame camera has been redesigned to work with the touch screen that can articulate.

Connectivity options on the Sony a7S Mark III include dual-band Wi-Fi, USB tethering, and a USB Type-C connector that supports SuperSpeed USB 5GBps data transfer.

Sony the global market leader in mirrorless professional cameras and competes favourably with other leading high end digital camera makers such as Canon, Nikon ,Fujifilms, Olumpus, Panasonic and Pentax.