Pauls0627@xxxxxxx wrote:
>
> I've been trying to get this full synchro flash stuff (and OTF flash in
> general) straight in my head (trying to convince myself to trade in an OM-4
> for a -4Ti, I guess!). Someone correct me if I'm wrong here:
>
> OTF Flash (OM-2n, OM-3Ti, OM-4, OM-4Ti):
>
> 1. First curtain begins to open, meter starts accumulating exposure off of the
> film and curtain
> 2. First curtain fully open - Flash fires
> 3. Meter quenches flash and starts closing the second curtain when sufficient
> exposure is measured (or flash fully discharges)
> 4. Second curtain closed - effective shutter speed 1/60
>
> I think step 4 is different for the OM-2 (not the -2n) in that the shutter
> will stay open as long as necessary to achieve sufficient exposure, even if
> the flash power was insufficient.
>
> Full Synchro Flash (OM-4Ti):
>
> 1. First curtain opens, flash begins discharging, meter starts accumulating
> exposure off of the film and curtain
> 2. When sufficient exposure is achieved, meter triggers the second curtain to
> begin closing, flash continues to fire
> 3. Flash stops when the second curtain is closed
>
> I assume the OM-77 handled full synchro flash the same way
>
> Full Synchro Flash (OM-3Ti)
>
> 1. First curtain opens, flash begins discharging
> 2. Second curtain begins closing to achieve shutter speed selected on ring
> 3 Flash stops when the second curtain is closed
>
> Notice that since the OM-3Ti's meter can't control the shutter, the F280 is
> acting essentially like a manual flash, therefore the need to do the GN
> calculations. In fact I don't think the OM-3Ti's meter is used at all during
> full synchro flash.
>
> I don't think it's possible for the camera to control the intensity of the
> flash based on an OTF reading, because it would have to adjust the intensity
> *during* exposure, resulting in different exposure on different parts of the
> frame as the shutter "slit" passes over the film.
>
> Since the output from the flash is constant, the only way to control the
> amount of fill flash is to vary the flash to subject distance (I think). I
> recall it was said here once that changing the exposure compensation dial on
> the OM-3Ti will provide varying fill rations. The way I see it, since the
> camera has no control over the flash other than to start it when the first
> curtain starts moving and stop it when the second curtain closes, changing the
> exposure compensation dial will only vary the total exposure, not the
> flash/ambient mix.
>
> Do I have this right?
>
> Paul Schings
> Coventry, RI
>
Paul;
I don't know if you have this right or not. I would like to know.
Maybe we should try sending this question to Vince or Pat at Olympus
Tech Support in NY?
(BTW, the last time I talked to Pat, month or so ago, he identified
himself slightly differently than usual, see if anyone can guess what
word has been added to his title?:
"Hi, this is Pat McFarlane, Olympus digital tech support")
--
george :>)
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