Trailing curtain I believe is a flash unit thing. The camera pulls the trigger to a low voltage. The flash will trigger when it is first pulled down, leading curtain just as it starts up, trailing curtain. On my K20D when I use the PC to my 540 or 500 trailing curtain works.
After rereading the whole thread I may be misleading (ie wrong). Trailing curtain is not only a part flash but is part P-TTL (at least on Pentax flash unit). If the flash is not in P-TTL mode no matter where the switch is on the flash is it will act like leading curtain if the flash is not in P-TTL mode. The misleading part is if you use the PC port the flash may say it is in P-TTL but will only be a dumb flash and put out full power.
DAZ
Last edited by DAZ; 11-29-2008 at 10:48 AM.