You asked
Is the canon ef 85mm f 1 4l is usm good in low light?
Yes, this is a strong low light lens. Its f/1.4 maximum aperture gathers a lot of light, and it's stabilised, which helps when you can't use a fast shutter speed. It's also a lovely portrait lens on full frame.
It really shines on a full frame body, and the sensor guide makes the case that full frame earns its place for low light and events. Good matches from the catalogue include:
On APS-C it frames like about 136mm, so it becomes more of a telephoto portrait lens there. If you're mostly shooting dim rooms on a budget, a fast standard prime is a cheaper place to start.
Written by Claude from this site's pages.