Originally Posted by
Dark Mist
You can use a faster than 1/180 shutter speed with your Pentax DSLR as long as the flash supports it.
All bodies since the K10D allow you to select Hi Speed flash synch if a flash with that function is mounted. The Pentax 540 and 360 flash units both do it and so do some Sigma and Metz units. Not sure about the ring flash but check the specs.
How it works is to strobe the flash for an extended period so that you get the full frame despite using a faster than flash synch shutter speed. Without it you would 'chop off' one side of your frame.
Hope this is of some help.