Modeling light

[Janice]

If you press the dof preview button on the 20d and 30d with your flash on...you get a modeling light.

This shows you where shadows will occur in your picture.
So whats the difference betweendoing this....and taking the actual picture (which will show you where your shadows are going to occur wont it?)

[Ally]

You get modeling lights on the big flash heads it just shows you were your light falls and how soft or hard it will hit your subject, Its more about the quality of light than the exsposure. HTH