It’s actually a rule you should use whenever and where-ever you’re filming, not just inside without lights, but it comes into its own indoors. Don’t fight the light (hmm… could make a good album name!), use whatever light there is in the environment to your advantage and don’t make things hard for yourself. I like to split this rule up into 3 “sub-rules” (no not sub-rolls!). These include:

Controlling the light by closing/opening blinds and curtains.

Utilising whatever electric lights are in situ (table lamps, overhead lighting, monitors/tv screens).