I hear photographers talk about the inverse-square law, particularly with reference to lighting. What is this law about, and most importantly, how is it applied to lighting for photography?
The more I read about this, the more confused I become. Illuminance, as I understand it, measured in lux, is the perceived brightness of light on a surface. It's what you'd measure with an incident ...
So, I was hanging out in the chat room, and hear mention of something called "Solid Angle". What is this, and how can it be important?