The new full-frame Exmor RTM backlit CMOS sensor with 12.1 effective megapixels16 has up to twice the readout speed of the α7S II’s sensor.
The camera lets you shoot internal 4K footage with 10-bit depth of field and 4:2:2 colour sampling when using Long GOP or All Intra compression.
Full-frame 4K recording at 120 fps19 with autofocus is possible. Each individual frame is recorded at a high bit rate of up to 600 Mbps.
For the first time, you can now record in the XAVC HS format with the MPEG-H HEVC/H.265 codec. This roughly doubles the compression efficiency. Compared to normal 4K XAVC S format, XAVC HS offers detailed 10-bit video with 4:2:2 colour sampling at similar or lower data rates.

More details in this manual.