Two sources shared some more info about the A7sIII camera. I thank them both! Disclaimer: The sources are testing prototype cameras. So some features might change or are not reported at all because of this.
Source 1 (first time source so take it with a grain of salt):
The new passive cooling system of the A7SIII will be a little slit on the right side of the camera (where all the ports are) which allows air to get in and out of the camera which allows it the be cooler because the camera isn’t completely sealed. Because it’s a passive cooling system, it will not make any noise or sound so it won’t interrupt audio when recording video. The passive cooling slit on the side has a mesh so the camera will still be weather sealed.
It will not have dual (native) ISO which more expensive cinema cameras have like the Blackmagic Cinema Camera 4k. It will, however, have a new sensor that has very fast read/transfer speeds (for the high frame rates (4K 120, 1080p 240).
We are currently shooting a video with the successor to the A7SII the footage out of this tiny beast is incredible we are shooting 4K 120FPS 10BIT 4:2:2 with 15 stops of dynamic range, our tests showing comparable to an Arri Alexa Mini
SAR note: I want to stress that the 15 stops dynamic range is a claim made by Sony marketing (if the rumor is true). Which means real DR might be a bit lower…
Rumored A7sIII specs recap (based on A7sIII protoype cameras)
- New 12MP sensor with fast readout
- records FHD 240fps, 4k120fps 10bit 4:2:2 and 4K120fps raw over HDMI
- 600mbps bitrate
- Base ISO 160 for S-LOG3
- no Dual ISO
- Max ISO 409600 (video)
- 16bit RAW output
- Sony claims 15 stops dynamic range
- world’s highest resolution new 9.44 million dot EVF (QXGA resolution)
- new kind of passive (noise free) cooling system with a mesh on the side to let air in??? (Camera still weather sealed)
- no overheating, no recording time limits
- UHSII card support
- Looks pretty similar to a Sony A7rIV.
- fully articulating screen like the one used by the Sony ZV-1.
- announcement late July
- shipment start mid August