Thanks again for the clarification. I checked the archives and use of the T20
in non TTL auto seems to be a source of confusion. You know your flash
units---I do have the Vivitar 283. I am still puzzled how the T20 can
modulate its output without help from the OM-2. I have been unaware of any
thyristor circuit in it. Thus how do you set the IS0 setting on the flash? I
believe the calculator dial just gives one the 2 available f-stops to set the
camera. I used my usual strategy given to me long ago in a sign in organic
chem lab "If all else fails, read the directions." This did not work in this
instance.
Mike
[OM] Re: Solution for slow synch speed for OM2 with fill-in flash
from Chuck Norcutt[Permanent Link]
Subject: [OM] Re: Solution for slow synch speed for OM2 with fill-in flash
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Thu, 11 Aug 2005 20:59:05 -0400
usher99@xxxxxxx wrote:
> Chuck and Andreas,
> Thanks for your input. I have read the T20 manual many times and alot of
> thing are implied and never
> stated. It was never clear there was an "auto"
> mode without TTL. There are two auto settings as you mention and I had
> assumed they controlled the
> max output and that the suggested f stops were not mandatory for it to work.
> (wrong) It appears that if the camera is in manual mode
> and the T20 in one of the auto modes, that this is non TTL auto.
Exactly. You nominally select one of the available aperture settings on
the flash and set the camera accordingly. You then set the ISO setting
on the flash to that of the film in the camera. This sets the flash
with exposure settings to equal the camera. You have to control this
manually since the the camera and flash do not communicate in this mode.
It sounds like if this fill-in with bright light is doable, I will
have to be very close.
> I do have a large Vivitar flash with a thyristor that does not talk with the
> OM-2. It has approx twice the GN of the T20, but states should be used in
> manual mode for fill-in.
You haven't given me the model number of the Vivitar flash but, given
that is has twice the power of the T-20 I'm going to guess that it's a
283 or 285. Regardless, the fact that it has a thyristor circuit also
tells me that this flash can also do non TTL auto. The whole purpose of
the thyristor circuit is to support non TTL auto. It's the thyristor
that allows the flash to quench its output at less than a full dump. If
it's a 283 or 285 it's like the T-32 in that it has 4 auto ranges
(aperture settings) instead of the two of the T-20.
> I supose one could calculate the appropriate distance for full manual and use
> the zoom to frame the picture properly, if possible. I also lost you on
> changing the ISO of the flash---does the OM-2
> contol this? Thanks,
Using the flash in manual mode is one way of doing it but not very
versatile. In manual mode the flash power output will be fixed. Since
you've already settled on shutter speed and aperture (to control for the
bright sun) the only means you have to adjust the flash exposure is to
vary the distance. Not so good since, as you suggest, you'll have to
zoom to do the framing.
Better to use the non TTL auto mode and let the flash vary the power
output. Since the flash unit has a fixed set of aperture ranges
available to it you can get more versatility by lying to the flash about
the ISO speed of the film. Set the ISO to double what's actually in the
camera and you'll get one stop less light output from the flash, etc.
Try it.
Chuck Norcutt
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