I just came back from a 5 hour shoot -- interviews shot in the vary spacious bedroom of a wealthy client. The room was very well lit with afternoon natural lighting coming in through the east-facing windows, camera right. The people being interviewed were well lit on the window side, somewhat in shadow on the camera-left side, the side away from the windows.
We tried using a reflector to bounce light from the window onto the shadowed side: window=key light, reflected (bounced) light=fill light. Back light coming from the windows, bouncing off the light tan wall behind the person being interviewed. Not enough fill, though. What to do?
We used a small dimmable camera light -- an NRG on-camera fixture -- on a low light stand, dimmed way down to create fill. Problem was, of course that the daylight side looked slightly blue/cold and the dimmed down light on camera left looked warm.
We solved this by putting a small bed-side lamp on a low table next to the client on camera left and turned it on with a low wattage bulb. This gave just enough light to show that the lamp was turned on; it cast a nice pool of light onto the table and side of the chair and motivated the slightly warm light on the client's face. We made sure to show the lamp at the beginning of each interview, just to remind the viewer that there was a warm light source next to the chair.
Once we balanced the daylight (key) and incandescent light (fill) the scene looked very good and completely believable.
The lesson to be learned here is one that film makers learned in the early days of film production: if you provide motivation for light by showing a source point -- a lamp, street light, flickering candle or fire, etc., almost anything you do with light and shadow that follows will appear believable. 20th century film noire gaffers and DPs used this principle in virtually every film.
Maybe you've had similar work-around experiences with lighting that you can share.