mail@xxxxxxxxxxxxxxxx writes:
<< Olympus used the technology from Minolta. Unfortunately, they stopped
further
developing it for OM after the F280 while Minolta continued. It made the
Super FP
5400HS flash with a Guide Number of no less than 54m, >>
This sounds almost a physical impossibility, since to achieve a GN of 54m
for normal flash requires an energy for a single short duration flash of
around 100J. In FP mode you need to have many flashes something like 20-30 so
since the energy available is what you can store in a capacitor at the start
of the flash the energy per flash drops proportionately giving you very low
GN's. To achieve a GN of 54m and provide say 20 flashes for the FP duration
would require you to store over 2000J. This is the territory of the very
largest studio flashes with line operation. My guess is the Minolta flash
achieves the 54m GN in normal flash mode and is significantly lower in FP
mode.
Interestingly Olympus does have a patent or two on FP technology but probably
not the primary patent.
A common question on this list is what reflectivity is used for simulating
film reflectivity on the shutter curtain and often people say that it is the
same as an 18 0rey card. One of the Minolta patents on regular OTF metereing
(US patent 3687026), specifies that a value of 26.7 hould be used.
Regards,
Tim Hughes
Hi100@xxxxxxx
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