Godfrey DiGiorgi wrote: > 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 >
I think it's 'digital' communication in this case, as rear curtain sync is one of the features only provided in Digital TTL or P-TTL modes with Pentax. With Nikon the issue is straightforward, rear curtain sync is set on the flash, and this has endured from the late 80's(when most camera/flash settings were set on the flash, a legacy of the F4's old-fashioned interface). -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.
