The concept of higher shutter speeds of Canon dSLR while using the 580EXII is quite similar to Olympus F280 flash with Olympus body...in both units, the short single pulse electronic flash is changed so that there is a series of rapid lower power pulses which appears to be 'one long duration flash' but which is simply a very rapid series of pulses. The implementation is likely to be different, so not directly compatible with one another.

As stated earlier, the FP setting of the PC socket switch factors in a short built-in delay to allow the FP flashbulb to ignite and achieve full output of light, before the shutter curtains move across the film plane.