[rollei_list] Re: Rollei Flash
- From: Don Williams <dwilli10@xxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 10 Jan 2008 14:11:54 -0600
At 02:46 PM 1/10/2008 -0500, you wrote:
From: "Eric Goldstein" <egoldste@xxxxxxxxx>
I suspect there is something to this. Part of the flashbulb look is
the longer burn time, which means less dead-on sharpness. A longer
shutter on a strobe shot might yield something similar with an kind
of ambient light level.
I also think film looks different when exposed to a 1/50,000 light
burst, which the longer exposure would mitigate as well (again, with
any kind of ambient light)...
Eric Goldstein
Not sure about the meaning of the term "dead-on sharpness" but there
is something to the flash duration issue.
Reciprocity failure (affecting effective film exposure) was a
significant factor in the early days of strobe systems. I think it's
no longer a big issue, due either to changes in emulsions or simply
accepting the fact that we lose a little of the energy from strobes
is just accepted and factored in.
Again, memory fails me but I do remember (from the late 1950's) when
building strobe lights for missile tracking that it was a concern.
For those not in the business then, the early tracking systems for
Atlas, Minuteman, and Polaris missiles included not only electronic
systems, but strobe lights carried on the missile and photographed
against the star background by multiple, open shutter "ballistic
cameras". Using the photographs from several cameras the launch
folks were able to compute the trajectory of the missile as a back up
to the electronic systems. The flash systems I designed used large
flash tubes, quartz windows at the missile skin, and ran 2 flashes
per second at 250 Watt-Seconds per flash until the bulb failed or the
one-shot battery blew. Lot's of fun in the lab!
DAW
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