Re: flash duration

[Thibs]

I seem to remember I read a couple years ago (so maybe it concerned old 
analog TTL) that some flash TTL systems were based on power variation 
when others were based on duration variation and of course everybody 
used one with Pentax alone using the odd one =D

I guess that modern system are bit of both.
------------
Thibouille
jayers a �crit :
Hey, the question was asked. The lower the output of the flash head the
shorter the duration.
Jonathan
-----Original Message-----
From: Keith Whaley [mailto:[EMAIL PROTECTED] 
Sent: Saturday, December 11, 2004 11:31 AM
To: [EMAIL PROTECTED]
Subject: Re: flash duration


jayers wrote:

Kevin the answer to your question is in Harold Edgerton's book
"Electronic Flash, Strobe" MIT Press. ISBN 0-262-55014-8
Flash duration is a complex subject it is measurable and is a function
of capacitance and voltage. Voltage and its duration are easily
measured
with an oscilloscope. 

C'mon, Jonathan...it's only "easy" if you know exactly what you're 
doing, and you have the equipment available!
To the rest of the great unwashed, it's a subject that ranges from the 
borderline arcane to the incomprehensible!  <g>

keith whaley

T=RC/2
T=time (microseconds)
C=capacitance in farads
R=E/Imax
R=resistance
E=initial capacitor voltage
Imax=Peak discharge current
To use this formula we would need to know the specification of the
flash
lamp.
All this and everything you will probably like to know about high
speed
light sources, and its application to photography is in this book. 
This is a complex subject which Edgerton passionately studied, and
developed practical applications. He shared his knowledge with any
body
that graced his door, and he has left us a great legacy in his book. 
Jonathan 

-----Original Message-----
From: Kevin Waterson [mailto:[EMAIL PROTECTED] 
Sent: Saturday, December 11, 2004 4:33 AM
To: [EMAIL PROTECTED]
Subject: flash duration

Is it possible to measure the duration of a flash?
Possibly in micorseconds or something?
Kind regards
Kevin