The Mamiya 645 Pro TL will not trigger the flash unless it is hooked up to both the flash synch cord AND the hotshoe. Is this correct? I tried it on the hotshoe alone (no synch cord) and it will not trigger the flash. Synch cord alone does not work either. BOTH must be used. This seemed strange to me, until I checked with the camera's manual, which confirmed that both must be used. I realize that I must use a bracket to use flash with this camera, but I cannot understand this about the hotshoe & synch cord. Or am I doing something wrong?