Xref: utzoo sci.electronics:4775 rec.photo:4269
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From: beyer@houxs.ATT.COM (J.BEYER)
Newsgroups: sci.electronics,rec.photo
Subject: Re: Flashbulbs (was something stupid and illegal...)
Summary: Camera flash contacts have delay for flashbulbs
Message-ID: <1134@houxs.ATT.COM>
Date: 18 Jan 89 14:00:21 GMT
References: <3835@midas.TEK.COM> <190700025@trsvax> <13355@cup.portal.com> <85595@sun.uucp>
Organization: AT&T BL Holmdel NJ USA
Lines: 29

In article <85595@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 = 0.4 = 1/250
> 
> Much slower than most cameras are capable of?
> I thought flash sync was limited by the shutter action??

For those cameras equipped with M flash contacts, there is a delay that
I believe is around 17 milliseconds between when the contacts close and
the shutter opens. At least, that delay for most flash bulbs.
For focal plain shutters, there is an FP type flashbulb (or there was,
I don't know if you can get them any more) that started burning before
the shutter curtain started to move, and burned at a 'constant' rate
until the shutter closed again. I find it hard to believe that they were
constant enough (I never used any), but maybe they were. On most 35mm
SLR cameras a focal plane shutter is used. Only an X (instantaneous) contact
is provided on many of these. Even my new Copal #1 shutters have only X
contacts. My old one can selece X or M. OK with me because I do not use
flash bulbs. For these, only very long exposures can be used with flash
bulbs because you want the entire shutter to be open for the entire useful
burn time of the bulb.


-- 
Jean-David Beyer
A.T.&T., Holmdel, New Jersey, 07733
houxs!beyer