Ambient light, ceiling fluorescents and window light. So very little processing is needed with this fabulous little camera...and I can't praise the 12-40 lens enough. It's just perfect for this venue in which I have to regularly shoot. So nice to be able to do my framing in the camera rather than wait for Photoshop. Shooting from my lap with a tap of the lcd is a dream for stealthy, natural looking candids. I feel under equipt when I have to use my dslr. (Rarely).