@ctrl-shift thanks, that sounds like a useful solution for single room renders. I suppose I'd start with the ambient room lights off and adjust the invisible window emitter until I get the lighting level I'd expect. It's going to be a huge job to set up every window in every room to work that way, though. I'd probably want to think about making the emitter a box with only the room facing facet using an emissive material, so I don't get outside bounces of light returning to the room when it's all supposed to be external ambient environmental light. I still want to be able to see the outside through the window, not pretend it's frosted glass. I'd also have to work out what to do when looking out of a window and seeing another externally lit room from inside the current room, though IRL that kind of thing is less problematic, as looking outside will usually constrict one's pupils during the day, so what you see through the window of an external room will be less visible that when you're looking at the interior of the room you're in. All complications of light adaptation affecting what one has experienced directly and therefore expects to see in a similar render. I'm also lighting the scene with a single, infinite sun light, during the day, whose position changes with the preset time. Matching that lighting would take some effort as well, to coordinate with emission levels of window props.