All my FourThirds and Micro-FourThirds bodies allow me to enable second curtain sync any time I want, with any flash. IIRC, both my Sony R1 and my Canon 10D allowed the same.
The algorithm is very simple: the flash is triggered about 300ms before the second curtain is released. So it obviously works best with exposure times of a half second or longer, but then that's when I'd use second curtain sync anyway. On Friday, July 2, 2010, Adam Maas <[email protected]> wrote: > On Fri, Jul 2, 2010 at 9:21 PM, paul stenquist <[email protected]> > wrote: >> >> On Jul 2, 2010, at 7:05 PM, Adam Maas wrote: >> >>> On Fri, Jul 2, 2010 at 4:53 PM, John Sessoms <[email protected]> wrote: >>>> The K-10D and K-20D both allow you to set the on-board flash to trailing >>>> curtain sync. How difficult would it be for them to make the hot-shoe also >>>> fire on the trailing curtain when a non-dedicated "flash" is installed? >>> >>> Very difficult unless certain assumptions about burn time are made, >>> which won't be accurate. You need to fire the flash at just about >>> exactly the burn time before the shutter closes for trailing curtain >>> to work corectly. Most speedlights have a roughly 1ms full-power burn, >>> but at low power levels it can be an order of magnitude shorter as >>> output is normally controlled by burn duration rather than intensity. >>> >>> Olympus did allow this on some OM models, but it only worked because >>> of the low sync speed of the camera's (1/60) so that even if the flash >>> burn time was much shorter than the assumed ~1ms you don't get much >>> exposure after the burn ends. This doesn't work so well with today's >>> high sync speeds. >>> >> Of course you can shoot trailing curtain synch at low shutter speeds on >> either the K10 or the K20. I get good results shooting trailing synch on the >> K10, K20 and K7 at 1/8th or 1/15th. >> Paul >>> -Adam > > low shutter speeds work better for non-dedicated flash and rear > curtain sync, it's at high sync speeds where the problem occurs becaue > the burn time is a much larger portion of the period the shutter is > open so a short duration burn triggered early nets you mid-curtain > sync rather than rear-curtain sync. With a dedicated flash it's a > non-issue because the burn time can be predicted and the flash > triggered at the right moment so it cuts off just before the shutter > closes. > > -Adam > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. > -- Godfrey godfreydigiorgi.posterous.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
