Recently we've changed from TTL flash to manual flash to experiment a little bit. A recent article in Professional Photographer magazine has me a little confused. There was a formula for how much power a flash requires based on distance and aperture. It doesn't seem like different flashes should behave the same at say 1/4 power. If you had a big flash at 1/4 power, isn't that different than a tiny flash at 1/4 power? Help me out guys!