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Re: [OM] F280 flash

Subject: Re: [OM] F280 flash
From: "Robert Swier" <rswier@xxxxxxxxxxxxxxxx>
Date: Thu, 18 Apr 2002 22:37:12 -0400
Ash...it's this kind of detail that I would have liked from the manual.
Knowing that Super FP mode does not provide auto exposure is a key piece of
knowledge.

Thanks,  William!

Robert Swier
Rochester, NY


----- Original Message -----
From: "William Sommerwerck" <williams@xxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Thursday, April 18, 2002 8:56 PM
Subject: [OM] F280 flash


> Several weeks ago I came across the manual for the F280, and realized why
it
> confuses everyone so badly. The manual is badly written, thoroughly
confusing,
> and downright misleading. So are the markings on the flash, which imply
that
> Super FP provides auto exposure, which it absolutely DOES NOT.
>
> I wanted to write a long explanation, but I don't have the time. For now,
> here's a quick rundown.
>
> The output of an electronic flash lasts from about 1/300 to about 1/3000
of a
> second. A small shoe-mount unit usually pops its capacitor load in less
than
> 1/1000 of a second.
>
> This is shorter than the fastest shutter speed of a leaf shutter. So the
> shutter speed in leaf-shutter cameras has no effect on the exposure
produced by
> an electronic flash -- only the aperture does. This allows the aperture
and
> shutter speed to be set independently -- the aperture for the amount of
fill-in
> desired, the shutter speed for correct ambient exposure.
>
> When an electronic flash is used with focal-plane shutter cameras, the
shutter
> has to be completely open when the flash fires, or part of the image will
be
> cut off. No focal-plane shutter can open fully in less than 1/250 of a
second.
> Most fall in the range of 1/100 to 1/125. The OM cameras have a relatively
slow
> flash sync speed of 1/60.
>
> This causes problems when using fill flash. The shutter speed can't be any
> faster than 1/60, which in turn requires a very small aperture, which in
turn
> requires a powerful auto-exposure flash (or a high-powered manual flash
with
> variable output).
>
> So... wouldn't it be nice if we could use electronic flash at speeds where
the
> shutter _isn't_ fully open? The only way to do this is to fire the flash
> hundreds of times, so that it looks as if its output is "continuous."
>
> When you switch the F280 from regular to Super FP, you convert it from an
> automatic flash to a _manual_ flash whose output lasts for about 1/50 of a
> second. (Despite what most people think, and what the switch on the F280
> implies, Super FP operation -- as far as the flash is concerned -- is
manual.)
>
> You can use any shutter speed from 1/60 to 1/2000, and the flash will
synch.
> But because the flash is now a "continuous" light source, you've lost the
> ability to set the aperture and shutter speed independently -- all
> EV-equivalent shutter-speed/aperture combinations produce exactly the same
> exposure from the flash.
>
> To put it another way -- when using the F280 for fill-in, you're stuck
with
> whatever the F280 emits. The only way to change the amount of fill-in is
to
> change how far the flash is from the subject, or some light-absorbing
material
> over the flash. This is why the F280 works beautifully in some situations,
> poorly in others.
>
> The chart in the manual can be useful in deciding how far you should stand
from
> the subject for "correct" fill-in.
>
>
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>


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