Light is fine.... I keep my rats in a room that has a window & a lamp. Im not sure what you mean I guess? They are not vampires
When I am in my room in the evening I always have the light turned on and my window's curtins are almost always open. Most people even keep their rats in their living room or main parts of their house.
I wouldn't have bright light shinging directly in their face. I wouldn't like that either though.