> > From: Rick Womer <[EMAIL PROTECTED]> > Date: 2007/02/19 Mon AM 03:13:27 GMT > To: Pentax-Discuss Mail List <pdml@pdml.net> > Subject: Re: *istD X Sync > > Peter, > > The ambient light should be contributing almost > nothing to the exposure under these circumstances. The > duration of the flash exposure is 1/1000-1/20,000 sec, > depending upon the exposure. X synch fires the flash > at the midpoint of the shutter's exposure. So, the > shutter speed should make no difference at all. > > Or is there something I am missing too? > > Rick
I think you may be missing the point about X-synch. It has nothing to do with the firing time, it's the fastest (shortest) speed that particular model of shutter will do where the second curtain does not move until the first curtain is fully open. Faster (shorter) speeds than X are produced by the shutter making a slit that travels across the frame. If you use ordinary flash (as opposed to high-speed, which is multiple bursts) at those speeds, part of the frame will be misexposed. The firing point, at X or lower, will be when the first curtain is fully open unless you have the option of firing as the second curtain begins to close, this being called "trailing curtain" synch. Apologies if you are an accomplished egg-sucker........ FWIW, "dedicated" to Pentax means the ability of the flash to talk to the body to set shutter speeds and affect displays. There are non-TTL, Pentax brand, dedicated flashes. > > --- Peter Loveday <[EMAIL PROTECTED]> wrote: > > > Am I completely missing something, or is there no > > way to set the *istD to > > its X Sync speed manually? > > > > I recall messing with this back when I first got it, > > but didn't really > > pursue it because the external flash I was using was > > dedicated anyway, so > > it'd work itself out. > > > > Now that its become part of my "second kit" since > > the K10D, I'm using an > > older (PC connection) flash... it all works fine > > (yes, I checked the trigger > > voltage), I'm using it in M, set the flash and > > camera to the same aperture, > > but of course I can only set the *istD to 1/125. > > > > In theory, X Sync is 1/150... but my other options > > (depending on half or > > third EV setting) are 1/160 or 1/180... > > > > Am I being thick, or does this seem really silly? > > > > - Peter > > > > > > -- > > PDML Pentax-Discuss Mail List > > PDML@pdml.net > > http://pdml.net/mailman/listinfo/pdml_pdml.net > > > > > http://www.photo.net/photos/RickW > > > > ____________________________________________________________________________________ > Yahoo! Music Unlimited > Access over 1 million songs. > http://music.yahoo.com/unlimited > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > ----------------------------------------- Email sent from www.virginmedia.com/email Virus-checked using McAfee(R) Software and scanned for spam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
