Does 4K impact quality when filming in low light? (other parameters being equal)?

Question

I'm wondering if **filming with a 4K camera, possibly downsizing to Full HD, will give better detail than filming with a Full HD camera** (other parameters being equals).Sub-question (maybe I should make it a different question?): - I have some more experience and better equipement for photography (Canon 6D),- I want my video camera to behave well in low light in moving environments,- I'm often filming moving things/people, I don't want much bokeh/focus loss (I never really remember if that means more or less depth or field).**I currently own a Sony Cybershot RX-100 M2.** Very unimpressive body size, but makes excellent 1920x1080x50p videos. I am thinking about an upgrade anyway, max budget for an outstanding camera would be 2000 EUR, but I am not sure if I want to put money in it right now since 4K market is still evolving fast, and so far I cannot really decide because other devices I got info about seem to be very similar or trade-off one advantage for another.For example compared to **Sony RX-100**, **Sony FDR-AX33** has a smaller sensor. Sony **FDR-AX100** only opens at f/2.8 and I use for a wider aperture, so has far as I know RX-100 would have a better low light score than both those cameras. **GH4** has more bokeh and seems kind of grainy in low light, ... and yet no camcorder in my budget has more than 30p with 4K.Suggetions would be welcome, because I cannot really tell what would be a serious upgrade or just wasted money.

Answer 1

"I'm wondering if **filming with a 4K camera, possibly downsizing to Full HD, will give better detail than filming with a Full HD camera"

Yes, shooting 4k typically provides better detail even when outputting to HD/lower resolution.

".Sub-question (maybe I should make it a different question?)"

Yes, the rest of this is a bit confusing, maybe try posting again with one or two clear questions.