Hey all, I was just wondering, what exactly is the difference between a standard Source Four lamp, a Tungsten lamp from say, a MAC TW1 or VL1000, and an Arc Lamp. I know it has to do with the gasses and other things inside the lamp itself. I really want to know the difference between an incandescent Source Four lamp and Tungsten. Why use one over the other? Color differences? I'd like to know.