----- Original Message ----- From: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, January 03, 2004 8:23 AM Subject: Re: Re[2]: OT: why trailing-curtain-sync is useful
> > And here I thought the flash circuit was simple and mostly > mechanical... Though I'll agree that the mechanism is a > bit tricky. Okay, more than a bit. > The main trick to the synch circuit is that the FP synch contacts act as the safety switch for the X synch circuit. The safety switch is open except when the shutter is being fired, because the X contacts remain closed until the shutter is cocked again. Thus an electronic flash won't be repeatedly triggering until the shutter is wound, or a fresh flash bulb won't immediately ignite. Pentax realized that most folks will be using flash bulbs for FP synch, and electronic flash for X synch, so the simple solution to the safety switch solution (for them, not having mirror lockup) was to put the FP contacts in series with the X contacts. For you this means that you have to disconnect the FP socket from the FP circuit, but leave the FP switch in there for use as the safety switch for the X circuit(s). The FP contacts are closed by the mirror as it rises, and then opened again when the mirror returns after the shutter cycles. Clever, those Japanese. > > Got everything but the scope. Here's hoping I can figure this > out with geometry, eyeball measurements, and trial-and-error, > or that I can borrow a scope. (Though perhaps sticking a > sensor from a digicam or some Polaroid film behind the camera > would be easier than trying to set things up to get useful > information from the scope...) > You shouldn't need a scope for this job, unless you want to CLA the shutter while you're in there. And that, as Frank and Doug used to say on SCTV, in another topic, for another day. Some back bacon and Moosehead are always handy, but not while you're working. ------ Robert
