--- Ken Durling <[EMAIL PROTECTED]> wrote:
<snip>
> it. I'm probably missing something obvious.
This goes back to the old days of flash and SLR's, the
Seventies! =)
> Cf.N 9 on the Elan 7 is titled "Flash sync speed in
> aperture-priority
> AE mode" and the two options are 0 = set
> automatically, and 1 = Set to
> 1/125th sec.
>
> Why would you want to lock the shutter speed to
> 1/125th in Av priority
> mode?
Believe it or not, in the dark days before the flash
set the shutter speed automatically, we had to
*manually* set the flash sync speed on the camera, or
risk "ghosting" (shutter speed too slow, camera shake)
or partially exposed pictures (shutter speed too fast,
only part of the focal plane slit exposed). I see this
as just being a carryover from those days. Since
electronic flash exposure are so brief, usually less
than 1/1000 of a second, it is the aperture that
controls the _flash_ exposure. Shutter speed controls
the _ambient_ exposure. If you want to get the flash
and ambient exposures right, you need to balance the
two, otherwise the background literally "fades to
black".
> Isn't that a form of "Tv priority?"
Absolutely not. It's a way of telling the camera and
flash to get the subject *flash* exposure right, based
on the flash output (as read by the TTL sensor) and
aperture, and let the ambient/background exposure fall
where it may, regardless of ambient light... if there
isn't much ambient light, it will just fall to black.
You are pretty assured you will not get ghosting this
way from the shutter speed going too slow. What you
are not certain of is getting a properly exposed
background.
> With the flash itself
> set to High speed sync, you can use any combination
> of aperture/shutter speed you want from 30 sec to
> 1/4000, so I'm not sure why this Cf.N is there.
This isn't exactly true, because for high speed sync
to work, the flash has to work stroboscopically, with
a pulse synchronized to the shutter curtain slit as
passes over the film. This drastically reduces your
flash range as the shutter speed climbs, as part of
the capacitor charge is used up for each pulse.
If the shutter speed falls below hand-holding range,
you will probably get ghosting, both from camera shake
and from subject movement.
I see the CF as a way of over-riding the default
behavior of the camera firmware, which wants to
properly expose the background in Av mode with
flash... if you don't have a tripod you'll probably
get ghosting if the shutter is too slow. Do you want
to risk ghosting, or risk of an improperly exposed
background? What's more important in the picture at
hand? That's the question the photographer has to ask
himself before he uses this.
MadMat
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