>re fill flash, Stephen wrote:
>
> ---------------------
>I've given this some thought myself, and I don't think ambient exposure
>would be affected. Assuming you set the "proper" aperature for a 1/60s
>shutter speed (which is what the camera sets automatically), using the
>exposure compensation dial won't (shouldn't ?) affect either aperature
>or shutter speed, only flash output. The flash output will be based on
>aperature, which the camera has no control over, and film speed. Thus
>ambient exposure (f<x> & 1/60s) should remain constant. Make sense?
>
Hi Stephen
I've fiddled a bit with this, and may well be wrong. Will try and
explain and hope this makes sense. Help from others may be needed!!
1. If camera is set to AUTO, and T20 set to full manual/control by
camera, you will get TTL flash, with the camera automatically using
1/60. So, let's assume your correct exposure is F8 at 1/60. Set your
lens to F8, flash on, camera fires at 1/60, you will get a correct
exposure with flash but flash may be too strong for your liking. So, to
underexpose flash by 1 stop (ie, to give a -1 fill flash), you dial in
-1 on the camera. However, the camera will automatically compensate
(while it is set on auto) and the shutter speed in the viewfinder will
now be 1/125! Which of course will mean your flash will not fire.
So! Set a correct ambient exposure for a speed of 1/30 at f11. Then,
dial in -1 like you did before. The camera will compensate since it is
set on auto, and your speed in the viewfinder will now be 1/60 at the
same F-stop (11). The flash will fire and the shutter speed will be
1/60. BUT, even though you will be getting one stop less flash light on
the subject, the exposure value for the background will be one stop
less. (1/60 at F11 instead of the correct 1/30 at F11). You will get an
exposure 1 stop less than correct ambient exposure as well as one stop
less flash exposure. I cannot see any way to get around this.
2. If camera is set on manual, you will not be able to use TTL flash at
all, even if you set the flash to "full control by camera". Your only
option is to set the flash to auto at one of the set F-stops, make sure
this is setting is one stop less than the f-stop of your lens (with
correct ambient exposure setting) with your camera set to manual. This
will give you correct ambient exposure with one stop less flash. There
are restrictions of course - you can only use the 2 pre-set auto
settings on the flash and depending on your level of ambient light, you
may be in trouble.
3. Set camera to manual, flash to manual, calculate distance and correct
flash exposure, then close lens down by one stop.
All done in a big rush.
Cheers
>Ashdown
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