At least one Nikon Speedlight has a mode in which it behaves like an FP flashbulb and allows flash sync with a focal-plane shutter at any shutter speed (not just the usual maximum speed for X sync.). Photographers have lost a useful resource now that there are no more flashbulbs - I seem to recall that bulb manufacturer's demonstration teams did things like photograph large public buildings (including the Great Pyramid) at night using 100 flashbulbs and more.