When I worked I was a Director of Photography. Light sources were always challenging when working on a location that had mixed light. If you didn't have a florescent flicker you had some light had had holes all over the spectrum. Just about all energy efficient lighting isn't natural. Even though your eye might not notice the difference, it is different and unlike any natural light source (sun, fire, starlight etc.) I've just always felt that after millions of years of evolution our bodies and brains don't like an unnatural light source.

May be full of s--t but I just made it a rule for reading.