Thank you again for your help.

Here is my current predicament: I have a rather unusual scene in mind, where only half of the environment seen through the camera is fully lit (as in daylight), while the other half is in the darkness.

I could do it by obscuring the light with something invisible, but the scene has some glass and water and other transparent things, so that doesn't help.

I could also try to limit the range of the lights I'm using, but the best way I know how to do daylight is through distant lights. I might need to go down this road, though.

I could also render it twice, but the scene is complex and my compositiing skills aren't the best. I was also pondering a possibility of a short animation, which with double renders is not going to be possible.