The D300 supports both shutter synchronized flash and FP flash at 1/320s

The first three photos show the different effect when photographing fast moving objects

The flash used is an SB-800

There are two issues when using shutter synchronized operation at 1/320s.

1> There is a one stop loss in maximum light output at this speed relative to slower shutter speed of 1/60s. This is because the shutter curtains are not open very long. So the camera limits the SB-800 maximum output to a 1/2 output flash at this speed. (However there is at least a two stop loss when using FP operation at 1/320s)

2> Even with the flash set to 1/2 output it's duration is still about 0.9 milliseconds. The shutter full open time is yet shorter than this. Consequently the second curtain starts closing while the flash is still firing. This causes a slight curtain shadow that can be seen in the gray card test shots.