You asked
Is the panasonic lumix s1 good in low light?
Yes, the Panasonic Lumix S1 is a strong pick for low light, mainly because of its full frame sensor. At the same framing and f-number, a bigger sensor collects more light, so images stay cleaner at high ISO. Full frame has roughly one stop of advantage over APS-C and two over Micro Four Thirds. The sensor guide explains the reasoning.
The lens counts for as much as the body. For dim rooms and night shooting, these fast options from the S1 list are worth a look:
Written by Claude from this site's pages.