Rome HBO series

[Tarbicus]

However, you really couldn't film interior shots if that's all you had, so considerable lighting is added. It would be interesting to hear from film professionals as to how much.

Actually you can, but it would take so much work and time to make sure it could be done the series wouldn't be made in the first place and they would have run out of money by the time Vorenus and Pullo had returned to Rome from Gaul.

The thing is it's all an illusion. The only thing that counts is what it looks like on the screen, including spraying black paint into corners that are too bright, and using clips and pegs on the off-camera side to make a suit better fitting. Probably the master of using natural available light is Clint Eastwood, which is how he normally (but not always) has his films lit - the good ones that is.