Well by now its probably preaching to the choir to stress the importance of a fundamental grasp of lighting principals. One of the principals you should understand is the law of inverse square as it applies to light. The better we understand the science of light and how it behaves the better we can then understand how to control its behavior. Microfilmmaker has published a great little tutorial on the inverse square law and how it applies to lighting. It should be noted that this law applies to point light sources, and that soft sources perform differently. Read the Full article here. You’ll find a relevant excerpt below.

ARTICLE EXCERPT:
by Tom Stern

You can cut the cost of lighting; use fewer and smaller lights, while still getting good exposures if you understand the Inverse Square Rule.

Inverse Square Rule

Here is the problem. Our vision adjusts so well to light and darkness, and compensates so effectively for poor lighting conditions, that it fools us. In the images above, a light is being moved back from a target. In the left-most image the light is shining brightly on a single square and is dumping about 100% of its light on that square. In the center image the light has been moved back some distance and is now falling on an area about the size of four squares. And in the image on the right the light has been moved back even further and it is showing on about nine squares.

Our intuition and our vision will tell us that if the image on the left is about 1 square wide and gets 100% of the light, then the center image, which is about 2 squares wide, then it must be getting about 50% of the light, and the image on the right, which is about 3 squares across, must be getting about 33% of the light. But our vision and our intuition would be wrong!

Read More to See Why You Would Be Wrong.