Thanks John. It behaves like I thought it would. What I thought about is the following: Use a non P-TTL flash as a 240FT set to 2nd curtain. It should flash only once. Find a way to make it of no use to the exposure but use it to trigger other flashes with optical sensor.
In theory, it should work. But I won't know before I grab my hands on the flashes.... 2010/11/1 John Sessoms <[email protected]>: > From: Thibouille >> >> I don't think so but would a K7 sync on 2nd curtain when used with >> X-sync cord (or hotshoe but not with a Pentax flash)? >> Or should I trick the Studio flash with pentax flash to fire them ? >> I can't test just yet and I'm curious ... >> > > I think the K7 works the same as the K10 & K20. > > The K10 & K20 do rear curtain sync with the pop-up flash, but there is a > pre-flash with the front curtain that will fool an optical slave. > > If there's a way to turn the pre-flash off when using the pop-up flash, I > have not found it. I've gone through the manual diligently. > > They won't do rear curtain sync with a hotshoe mounted flash except for the > AF-360FGZ and AF-540FGZ, both of which also have pre-flash on the front > curtain. > > The K10 doesn't have an X-sync (PC) socket. > > The K20 manual seems to indicate you can have rear curtain sync through the > X-sync (PC) socket, but it still has the front curtain pre-flash when I > tested it. > > I tested using a CyberSync connected to the PC and a Vivitar 285HV set to > 1/16 power on a Quantum Battery One to get a really fast recycle time. > > I couldn't get a "rear curtain sync" flash off the PC with a shutter speed > faster than 10 sec. > > And with a 30 sec exposure I got 4 flashes. I think the K20 just closes the > X-sync (PC) circuit and leaves it closed until the rear curtain starts to > close. So, what I'm seeing is the CyberSync transmitter's re-cycle time > instead of the rear curtain sync. I get another flash about every 8 seconds. > > If it is just flashing every 8 seconds when the CyberSync recycles, I should > get another flash at 32 seconds if I use Bulb ... and lo & behold it comes > in right on schedule at 34 seconds. > > If you had a circuit that would trigger the flash when the X-sync (PC) > socket circuit opens you could probably get rear curtain sync with the > X-sync. I don't know how to build one, and I don't know where to buy one, > but now I know what to look for. > > I don't know if the K7 works any differently than the K20. > > Both manuals (K20 & K7) have the same statement regarding rear curtain sync > with the X-sync (PC) socket: > > "To prevent vignetting caused from Trailing Curtain sync, it is recommended > to take a test shot using a shutter speed one level slower than the flash > sync speed." > > -- > 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. > -- Thibault Massart aka Thibouille/Thibs ---------------------- Photo: K-7, Sigma 28/1.8 macro, FA50/1.4, DA40Ltd, K30/2.8, DA16-45, DA50-135, DA50-200, 360FGZ ... Laptop: Macbook 13" Unibody SnowLeo/Win7 Programing: Delphi 2009 -- 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.
