Originally posted by Lurch I run a Sigma 530Super and it goes like a champ.
Try shooting HSS with a K-3 and 530 Super. Mine will not fire above 1/180s mounted on a K-3, and will fire in HSS (FP) mode on a K20D using identical settings.
Originally posted by awaldram however WR a flash would be I'd feel exposed shooting with 25,000V two inches from my nose in the wet
I expect that high voltage on a flash is pretty harmless. You may get the equivalent of a static shock. Current is what makes electricity dangerous, and there's very little of it in a flash gun (i.e. milliamps). The only way low current can harm you is if it is connected directly to your bloodstream and routed through your heart, as in some medical treatments.
Originally posted by rawr I can report that the standard Sigma 530 DG ST works fine on the K-3, bounce flash and everything, so the DG Super probably will too.
I don't doubt the 530 ST functions all operate flawlessly on the 530 ST, but it does not have capability for HSS or Wireless. The 530 Super is supposed to have these extra functionalities, and Wireless works as intended. HSS, on the other hand, is not available with the 530 Super on a K-3.
I've used the 530 Super on several older Pentax bodies, with full functionality. I don't know whether the newer Sigma 610 Super would be fully functional on a K-3.