Sony A7s II is great for shooting documentaries (due to its low light capability) and for films (due to its 4k capability with Slog 3)
It is markedly improved over the A7S. The newer version adds
– Built-in 5-axis image stabilization
– Records 4K video internally with full pixel readout (on SDXC memory cards)
– Records S.log 3
– Bigger Magnesium Alloy chassis gives better grip
Video record button can now be set to a function button 
Other advantages
– High ISO – 100-102,400. Goes upto 409600. (Good results upto 64000)
– Built in wifi capability to connect with a smart phone or tablet
– Records 120fps at full HD
– Possible to charge the camera via USB port
– Sensor – 35 mm full frame (35.6 x 23.8 mm), Exmor CMOS sensor
Recording format
– A7S II uses a 12.2MP full-frame chip (4,240 x 2,832 pixels)
– Records on XAVC-S codec at 3,840 x 2,160/25p at 100 Mbps / 8 bit
– Colour sampling 4:2:0
Lens Mount: E-mount
Audio In: 3.5 mm Stereo minijack
Audio Out: 3.5 mm Stereo minijack
Video Out: micro-HDMI
Battery: Rechargeable battery pack NP-FW50
