Xref: utzoo sci.electronics:4777 rec.photo:4272
Path: utzoo!attcan!uunet!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics,rec.photo
Subject: Re: Flashbulbs (was something stupid and illegal...)
Summary: Flashbulb timing
Message-ID: <2942@kitty.UUCP>
Date: 18 Jan 89 22:28:36 GMT
References: <3835@midas.TEK.COM> <190700025@trsvax> <13355@cup.portal.com> <85625@sun.uucp>
Organization: Recognition Research Corp., Clarence, NY
Lines: 35

In article <85625@sun.uucp>, emartini%joey@Sun.COM (Ed Martini - Graphics Software) writes:
> > > 15 milliseconds, with the effective photographic illumination being
> > > extinguished after an additional 25 or so milliseconds having elapsed.
> > 
> > 	.015 + .025 = 0.04 = 1/25
> > 
> > Much slower than most cameras are capable of?
> > I thought flash sync was limited by the shutter action??

	I am looking at a book which has light output curves of various
flashbulbs.  There seems to be three timing parameters: (1) half-peak time;
(2) peak time; and (3) effective duration.

	Looking at the curve for an AG1B, there is essentially zero light
output for the first 5 milliseconds.  The half-peak time (i.e., elapsed
time from firing) is around 8 milliseconds where light output reaches
about 225,000 lumens.  The peak time (i.e., elapsed from firing) is
around 14 milliseconds, where light output reaches about 450,000 lumens.
The effective duration time is around 20 milliseconds (i.e., from beginning
half-peak time to ending half-peak time).

	So far, we have elapsed about 28 milliseconds.  At 40 milliseconds
total elapsed time, there is still around 50,000 lumens of light - no where
near peak, but not insignificant either.  Total light extinction occurs
at an elapsed time of around 46 milliseconds.

	With X-synchronization there is virtually no shutter delay, and
the spec says the shutter must be at least 80% open 1 millisecond after
firing.  With M-synchronization there is a shutter delay, and the spec
says that the shutter must be fully open by 15 +/- 2 milliseconds.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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