I have an old Pentax *Ist D with an old Sigma external flash unit with difuser. The Pentax is having a few troubles (using the on-board flash tends to run the battery dry in several shots, and the auto-focus sounds a bit grindy) and my wife purchased a new Olympus E-420 for me. I preferred using the external flash unit previously on manual only, anyways. Is there any way to use my old Sigma flash unit on my new Olympus? I understand TTL and all that won't work, but will it still set the flash unit off to flash on the press of the shutter (as the main electrical point on the hot shoe and flash connects) if it's in manual mode? It may sound like a stupid question and a bit cheap, but if I have a half-way decent flash lying around not being used and it can be, then why not?