modeling flash?

[Tom3]

On the D200, with the flash on, if I press the Depth-Of-Field preview button, I get the flash unit to 'buzz' and emit light for a second of so. I see the doc calls it 'modeling flash', but what is it used for?

 

[Big Mike]

This is so that you can visualize what the flashed photo will look like, check the shadows etc.

A typical studio strobe has a regular bulb that is the modeling light. It's not used for the exposure but is on so that you can see what your light is doing.