------- Forwarded Message Follows -------
Date: Thu, 29 Jul 1999 06:30:51 -0700
Date: Thu, 29 Jul 1999 08:32:14 -0500
To: olympus@xxxxxxxxxxxxxxx
From: Joel Wilcox <jowilcox@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [OM] Flash/lens question
>
>I have recently aquired a Vivitar flashgun the model is a 3500 Zoom Thyristor
>and apparently it is Olympus dedicated. It cost me ú10 but what I didn't get
>was
>any manuals etc.
Alex, one never does! It's a rule. ;-)
>Is anyone familiar with this flash gun? ...it's in two parts that couple
>together, the lower part has a hole at the front, a switch at the side that
>turns on a beeper when the flash is ready, and another switch at the back
with
>three cloured dots (red, orange and blue) a yellow triangle and TTL there
is a
>green LED that I can't get to light up. The upper section has the flash unit
>(bounce head and a zooming diffuser) and a scale at the back with lines that
>correspond to the dots on the lower section, and a sliding ASA scale. (and
>houses the batteries, on/off switch and light that indicates the flash is
>ready).
>
>Does 3500 mean a guide number of 35(m) at ISO 100?...and what is a
>"Thyristor"??!
>
I don't have any technical knowledge of thyristor circuitry, but it means
in crude terms that there is something like a capacitor that prevents you
from burning your batteries all the time that the flash is turned on. You
may see the ready light go from red to green. Red means it's ready to fire
but still on battery; green means it's also ready to fire but not burning
batteries at the moment.
I'm not sure of the GN for the 3500, as I own different Vivitar flashes. I
hope Brian Huber will weigh in here as he's been helpful with questions on
this flash. If you put the manual scale to the proper ASA, multiply the
number of feet indicated for, say, f8 times 8 and it will give you the GN.
E.g., f8 x 10 ft = GN 80. That scale thing is basically simple slide rule
predicated upon the flash's GN.
If you are using the flash with an OM-2(X) or OM-4(X), you can put the
switch to TTL and get TTL/OTF control by the camera in auto mode. Use the
Exposure Comp dial to tune your exposure for non-neutral backgrounds or
foregrounds. If you switch to manual mode on your camera, the flash on TTL
will do a full manual dump.
With the OM-1 the colored dots represent the different auto settings
controlled by the flash module itself. Set the f-stop as indicated. The
yellow triangle is for use with a motor drive. To use this you have to be
rather close to the subject because you'll have to open up the aperture as
much as 5 stops from the indicated manual setting. I don't remember the
specifics but it can support motors which are faster than OM provides.
Good luck with that. I've never used it.
Joel Wilcox
Iowa City, Iowa USA
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