The magic with flash on the OM-3t is being able use TTL flash while
also using slow shutter speeds to fill in the background. You can
compensate the amount of (fill) flash light with the exposure
compensation dial. As you note, taping over the contact on the OM-4t
allows the 4t to do flash auto exposure at lower shutter speeds, but
the auto exposure mode will adjust both the speed and the flash, while
in manual mode with the 4t (and contact taped over) you will have to
use guide numbers or use the flash's internal auto exposure control.
The 3t is manual speed even with TTL auto flash exposure, so you can
use the flash with OTF exposure while controlling the amount with the
compensation dial.
I just did an experiment with the OM-4t and contact taped over. I used
a flash meter to check the result. With the contact taped over, camera
in auto, and memo activated to record the actual shutter speed. The
meter said normal exposure should be 1/4 second. With the flash firing,
the actually speed was almost 1/60th. This makes sense, the flash fires
when the shutter is fully open, gets enough light and closes, result:
the shutter sync speed. (note you need a piece of film in the camera.)
So you can't quite do what the OM-3t does - TTL flash control with
manual speed. With the 4t, you have to use the flash's auto exposure
with camera in manual mode to do the same, not TTL OTF flash.
Wayne
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