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Re: [OM] More Calcs on Flash GN

Subject: Re: [OM] More Calcs on Flash GN
From: HI100@xxxxxxx
Date: Wed, 8 Mar 2000 04:32:06 EST
Dear OMer's,
                      a periodic question that appears here is:  What is the 
relationship between Flash GN and stored energy in the Flash capacitor? This 
depends on reflector efficiency, area of coverage and flash tube efficiency. 
Here is a comparison between the OM  T20 and T32 flashes showing that despite 
the differences in flash tube,reflector and stored energy the overall 
efficiency is almost identical. 

T32 Flash energy  70 Joules (or Watt-secs)        GN 32 (m)    coverage 24mm 
Lens
T20 Flash energy  25 Joules  (or W-s)                GN 20 (m)    coverage 
24mm Lens

We expect the flash energy per unit area to decrease as the square of the 
distance. (Area covered increases by square of distance)
So the T32 should theoretically produce a light intensity identical to a T20 
at a distance of square root (70/25) = 1.67 greater than the T20.  
Thus the T32 GN should theoretically be 20*1.67 = 33.4 which is close to the 
nominal 32. 
The T45 apparently is two T32's sharing a common reflector which would then 
be 140J and have a GN  32*sqr root(2) = 44.8  
pretty close to the nominal 45.

Coclusion the overall conversion efficiency of all of the OM T flashes is 
essentially identical.

Regards,
       
          >>   Tim Hughes  <<

          Hi100@xxxxxxx
          






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