The Aurora Chasers | a7S II test footage of Northern Lights at 40K ISO in S-Log3 in 4K UHD @TheAuroraChasers | Uploaded October 2015 | Updated October 2024, 1 day ago.
Tech details at the bottom.

Testing the Sony a7S II with internal 4K capture and in S-Log3 Profile. It seems to have less banding issues and the IBIS (in body image stabilization) are really nice. Not having to lug around the Atomos Shogun which doesn't play nice in the cold will be nice as well. That said, it still has issues. At least in S-Log3 I didn't see a real improvement in ISO performance. It still has the obnoxious red corner issues and battery life is maybe worse than the original a7S. It's certainly an improvement overall and more testing remains to be done but if I'm honest, I'm a bit underwhelmed. Is it worth the price, certainly! The internal 4K, the IBIS and the 120fps in 1080 alone are worth the upgrade. I'm hopeful as I dial things in, I'll get a bit more out of this camera than I was with the previous model. Stay tuned.

Sony a7S II
Rokinon 24mm f/1.4 Cine lens
ISO 40,000
1/25 sec
24fps
Shot is Picture Profile 9 using the defaults which are S-Log3 and the S-Gamut3 Color Mode.