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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