On Oct 14, 2007, at 2:47 PM, mike wilson wrote: >> For effective second curtain sync actuation, all that is required is >> that the camera send a trigger signal to the flash at most .004 >> (1/250) second before the second curtain is released for its closing >> run. That's the typical longest electronic flash duration of a >> professional studio flash. >> >> Nothing 'smart' is necessary in the flash at all. > > Absolutely true. It used to be done mechnically from the camera body > with a second set of contacts interacting with the closing curtain. > This, of course, required the extra contacts and a switch to use them. > Digital flashes can obtain the information from the (robo)camera. > This, > of course, requires the programme in both units to be able to make > sense > of the photographer's desires. > > Sometimes, I feel this is where digital lets us down.
I don't know what "digital" has to do with it. Since the flash trigger is 100% transistor controlled nowadays and under the control of the camera's shutter, itself timed electronically with a computer driving it, second curtain sync doesn't need any additional contacts in the flash mount or shutter, nor any other communication between the camera and flash unit. All the body has to do is know what shutter time is selected for an exposure and that first or second curtain sync is required. Then the body delivers the flash trigger signal at the appropriate time: either when the first curtain reaches fully open or prior to releasing the second curtain with the correct minimum lead time. The simplest, dumbest flash just goes "pop" when the trigger circuit is closed. This is *exactly* what the Sony R1 digital camera and Panasonic L1 digital SLR body do. They work with my Sunpak 383 and any other non- dedicated flash for second curtain sync beautifully. I'm mystified that Pentax didn't do the same and rely upon additional communications between flash and body to permit second curtain sync. Godfrey -- 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.
