Robert M. Gary writes:

Passengers and cargo have little to do with it. You're probably
confusing commercial with 135.

I'm making a distinction between flying for hire and flying for one's own
business purposes. Just as a private pilot can fly between his offices in
different cities for business purposes, he can fly for the purpose of taking
pictures. If he transports someone _else_ who acts as photographer, though,
the situation may change.