OK guys...
Well perhaps I have it wrong...
Correct my arithmetic:
1 joule per second is a watt.
1 watt second is 1 joule per second for 1 second
500 watt seconds is 500 joules per second for 1 second
(or in the case of a theoretical flash unit, its 500 000 joules
for 1/1000th of a second)
A 500 watt lamp, burning for one second is 500 joules too so a
1-second exposure should give the same amount of energy (light) to the
sensor/film as a single burst from a 500 ws flash.... 500 joules????
Where did I go wrong?
My point was:
In a perfect world, a single burst on a 500 WS flash unit should
require the same aperture as a 500W tungstren light at 1 second
exposure which is also 500 WS.
(Not allowing for the inefficiency of the tungsten lamp)
A good part of the energy is given out as heat in both systems so
it becomes impossible to actually relate watt-seconds to light output.
Herschel Mair
Head of the Department of Photography,
Higher College of Technology
Muscat
Sultanate of Oman
Adobe Certified
instructor
+ (986) 99899 673
-----
Original Message ----
From: Qkano
<wildimages@xxxxxxxxxxx>
To: List for Photo/Imaging Educators - Professionals - Students
<photoforum@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Friday, February 9, 2007 2:58:09 PM
Subject: Re: Watt-seconds in flash
>Ah Roger... read it again:
>
>>No! Watt-seconds is just that. Watts times seconds. It's a
measure
>
>That's exactly what I said... allow me to do the math for you:
Hershell
I thought you had it wrong too I'm afraid.
I understood the correction watts.seconds was much clearer.
Bob
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