Aiya, this can be achieved quite a while ago via lumias and eventually phone cameras with slow shutter like find7. Vivo xshot which is almost a year old have manual shutter too.
Just that finally a bigger brand with much better marketing power is doing it now.
I played with G4 in a fairly lowlight room in yellowish lights setting on last Tuesday.
In general, great phone.
Camera wise, I find the manual mode a bit too cluttered and the shots are way way over processed. The water painting effect is quite bad.
S6's shots are over sharpened although they are toned down compared to note 4 but in comparison to G4, G4 is way more artificial. I guess raw is a solution but the majority wouldn't be bothered.
Shot to shot speed and efficiency wise, G4 is noticeably slower to s6 but is still fast.
In conclusion, what attract me most to G4 is the screen to phone size ratio, best in market!