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Re: [OM] More Calcs on Flash GN

Subject: Re: [OM] More Calcs on Flash GN
From: "Rand E." <rtomcala@xxxxxxxxxxx>
Date: Wed, 08 Mar 2000 06:43:58 -0500
Tim,
  I must take the part of the devil's advocate on this.  I concur with
all your logic and computations as "fact is fact".  The area where we
part is that all your data is factory given (optimistic ?) It is a well
presented design concept.  Has anyone tried this with "actual" data ? 
What are the results ?  Just looking at it differently.
Rand E.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
HI100@xxxxxxx wrote:
> 
> 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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