It's been many years since I've actually used a T32 on-camera. When I
did I alwyas used it with an OM-2Sp and in TTL mode or my OM-1 in auto
mode (I didn't know any different back then). Prior to this morning I
don't think I've ever paid much attention to using the T32 in manual
mode much less as a manual direct flash.
I've grown attached to my Canyon 540EZ for that sort of usage because it
has a built-in distance calculator bar graph when in manual mode which
does all the guide number calculations. The flash communicates with the
camera and knows the ISO setting and the focal length and shooting
aperture of the lens in use. If allowed to do so it will also zoom the
flash head to suit the lens. When it does all of this it also displays
the f/stop in use and a distance scale. Above the distance scale it
puts a marker over the distance that should be used at that focal
length, aperture and ISO. You can either position yourself at that
distance or choose to change the zoom head by changing focal length or
change ISO or aperture to get the right exposure.
So, this morning I decided to see what assistance the T32 offers for
manual guide number calculations. After looking at the calculator panel
I realized that I wasn't 100% sure about how the distance scale was to
be used in manual mode. I think it may have been the first time that
I've ever completely read the T32 manual.
As it turns out the distance scale in manual mode is meant to give the
correct guide number calculated distance vs. aperture when the ISO is
set with the flash at full power. At ISO 100 the guide number is the
nominal 32 meters and reading the scale for a distance of 8 meters says
to set the aperture to f/4. To double the distance to 16 meters at f/4
we'd have to quadruple the ISO to 400. So far so good. But what
happens when you change to low power manual mode which changes the guide
number to 16 from 32 at ISO 100. The Canyon will do all the calculation
automagically but the T32 manual doesn't even give any guidance on what
to do. I pondered this for a second until it finally dawned on me that
the solution is to simply lie about the ISO level. While cutting to the
low power mode of the T32 halves the guide number from 32 to 16 it is
actually cutting the power level by a factor of 4. To compensate on the
guide number calculator dial we only need to cut the ISO setting by a
factor of 4. So, if you're shooting with ISO 100 film just set the ISO
on the dial to 25. Now the calculator panel will read correct distances
and apertures at the lower power setting.
Dr. Flash
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