>1) With an OM-4ti...
>
> a) Let's say I have a T32 flash.
> I switch the camera to auto, set the flash to TTL. I meter the ambient
> light, set the aperture for a value that allows a shutter speed of
> 1/60th or less. Let's say I'm using Reala, and f11 works. ASA100,
> 1/60th @ f11. (But does the 4ti automatically switch to 1/60th?)
Kind of. With a dedicated flash the 4ti will not use a shutter speed longer
than 1/60.
> change the _ASA_ setting (not exposure compensation) to ASA 200.
Doesn't matter whether you change asa or dial -1, it gives the same result.
> Take the photo. This gives me a fill of one stop under ambient light. Right?
No. The camera thinks it has an extra stop of light to play with ... so shutter
speed at f11 is now 1/125, and the camera doesn't fire the flash at all. Damn -
a photo 1 stop underexposed!
>OR...if I know I want TWO stops under, it looks like the T32 has a 1/4 power
>setting.
Nope... this only works with the flash in manual mode.
> Or is there a simpler way (I hope)?
Yes... there is, but you won't like it... buy a 3ti (ouch!!), set the exposure
manually, then use the exp. comp to turn down the flash. Maybe that's why
they're so expensive.. ;-)
>I think what's confusing for me is how the TTL-OTF flash, and auto mode of the
>camera, interact.
They don't interact, cos they are the same thing. In auto, the ttl sensor looks
at the film (or opening 1st curtain) until it has seen enough light. If it sees
enough before the 1st curtain is fully across, it releases the 2nd curtain and
the flash never gets to fire. If it hasn't seen enough, it fires the flash. It
then continues to measure the light reflected from the film - remember it can't
tell whether this is ambient or flash light - and when it has seen enough, it
quenches the flash and then shuts the 2nd curtain. If it hasn't seen enough (ie
the flash discharges completely) it shuts the 2nd curtain anyway. You can
prevent this by covering one of the flash contacts with insulating tape - then
(as with the original OM-2) if the flash isn't enough it will hold the shutter
open until enough ambient light reaches it (up to 4 mins max).
So there is no way to alter the balance between the flash and ambient light in
auto - the 4ti is from a generation before auto fill-flash. So its back to the
tables, or ...
In auto, my KISS technique is to set the aperture so that the shutter speed bar
is just (1/3 -2/3rd)to the slow side of 1/60th. Without the flash turned on,
this would result in the camera exposing the scene at about 1/50th. Turn the
flash on, and by the time the 1st curtain is open, the sensor has already
almost seen enough light to satisfy it. It turns the flash on, which then only
has to 'top-up' the ambient exposure, resulting in a fast quench and little
flash released. I've no idea what ratio results (it would be affected by
distance) but it seems to work reasonably well. Perhaps someone with a
flashmeter could measure the output?
For important scenes, it's manual all the way. (I can't afford a 3ti either...)
Hope this helps,
Adam
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