Xref: utzoo sci.electronics:4774 rec.photo:4266
Path: utzoo!utgpu!attcan!uunet!lll-winken!ames!sgi!donl@glass.SGI.COM
From: donl@glass.SGI.COM (donl mathis)
Newsgroups: sci.electronics,rec.photo
Subject: Re: Flashbulbs (was something stupid and illegal...)
Message-ID: <25113@sgi.SGI.COM>
Date: 18 Jan 89 20:22:09 GMT
References: <9844@sequent.UUCP>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 28

In article <9844@sequent.UUCP>, brian@sequent.UUCP (Brian Godfrey) writes:
> >> 	.015 + .025 = 0.04 = 1/25
> >> Much slower than most cameras are capable of?
> >> I thought flash sync was limited by the shutter action??
> 
>    To sync to a flash you must make sure the shutter is all the way open
> before the flash fires (begins emitting light.) To get reproducible
> ..
>    Electronic flash is extremely fast, ranging generally from 1/5000 to
> 1/25000. With electronic flash you have to make sure and wait until the

Many electronic flashes fire much slower, often less than a 1/1000,
particularly larger studio flashes.  On-camera flashes shut down much
faster when less light is required.

> Leaf shutters open very quickly, so you triggered the flash then waited
> for most of the 15 milliseconds before opening the shutter. Focal plane

It's my understanding that leaf shutters trigger the flash when they
are fully open, at least on X-sync (which is the only option on my Copal
shutters, and on my dad's Seiko shutters).  The time spent opening and closing
is therefore irrelevent, as far as the flash is concerned.
--

- donl mathis at Silicon Graphics Computer Systems, Mountain View, CA

{sun,pyramid,adobe,decwrl,ucbvax,allegra}!sgi!donl
donl@sgi.com