A99II 4k Sample in Low Light
 

I haven't had a chance to film a proper test, but here's a short clip showing a variety of settings as I rushed to get B-roll on this car done before it was too dark.

Contains various shots using full-frame and Super35 modes, ISO from 800 to 2500. Some shots with stabilization on. Focusing all done manually.

Filmed with the following:
Sony A99II
Sony Zeiss 24mm f/2
Sony Zeiss 50mm f/1.4
Sony Zeiss 135mm f/1.8