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 > > -- > 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.
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