"If you're doing FP flash synch at 1/500 sec, isn't that LESS energy used than
at 1/60? I know the FP burst is spread out longer than regular auto flash, but
still, 1/500 is 1/500."
No, it's not -- not for focal-plane shutters. In OM cameras, the shutter's
"speed" (the time it takes for the first curtain to traverse the film plane) is
always 1/60 of a second. The effective exposure time is controlled by how soon
the second curtain is released after the first. So if you want to sync flash at
1/500 of a second, the flash duration has to be at least 1/60 of a second.
The Super FP flash duration is _always_ 1/50 of a second, presumably to allow
the tube's output to reach "maximum," and to minimize any sync-timing errors.
As far as I know, the F280 fully "dumps" the capacitor into the flashtube
during manual or Super FP mode. (Super FP is just a different form of manual
exposure.) This means Super FP will eat batteries faster than auto operation.
I'm certain the F280 is a thyristor flash; it doesn't dump the excess capacitor
charge in auto operation. So, for a given film speed and aperture, the closer
you are to the subject, the faster the flash should recharge in auto mode.
Manual and Super FP would always have the same recharge time, the maximum.
"As the shutter curtains travels at a fixed rate (only the slot size is
different), I expect that the energy used to provide light during the
period of travel of the shutter curtain slot would be the same at 1/60 or
1/500. Or have I misunderstood the principle of FP flash (same as FP bulbs)?"
Bingo. You've got it.
"You are partially right, I just made it too simply, I know the camera adjusts
shutter speed according to flash reflection from the film/curtain. But the
flash is under controlled, the flash duration is from 1/25 to 1/50 on the OM4Ti
and 1/30 to 1/70 on the OM707. It depends on the shutter speed reading from the
sensor/2nd mirror reflection (not OTF)."
Where did you find this? I've never seen it in any Olympus documentation. If
this is true...
"It makes my head hurt just to think about it. The F280 manual has a chart that
shows increased range for the flash with higher film speed, larger F stops and
slower shutter speed...
Which is exactly what you would expect for any "continuous" light source
mounted on the camera...
"Of course with with higher film speed the automatic exposure system will
operate to decrease the light coming into the camera from both ambient and
flash sources. I guess you carry the chart."
Super FP operation is designed principally for daylight fill, yet Olympus never
addresses the issue of how to use it to achieve the desired results. As far as
I know, the chart is for "full" exposure, not fill. Of course, there are no
walls outdoors to reflect light to the subject, so actual exposure will be less
than the chart shows, but (again) whether it's what you want is something you
can only determine by experiment.
Super FP is a lot like multi-spot metering -- both are terrific ideas, but they
don't _quite_ work they way you think they "should," and they require some
thought and experimentation to get the most out of them.
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