I think your problem is that you're trying to get the camera to perform
the flash's function. Without TTL control of the T-20, the camera has
nothing to do with the flash exposure. It can't measure the flash
exposure nor can it control the flash in any way except to initiate the
firing of the flash.
The only form of automation that you have is the auto mode on the flash.
When the flash is in auto mode it will control its own output to make
what it considers a proper exposure. To make this work properly the
camera should be in manual mode with a shutter speed less than or equal
to the E-1's sync speed which is 1/180th second. The longer this
shutter speed the greater the addition of ambient light to the flash
This may be the cause of the overexposure you're seeing if you have the
camera in auto mode. In auto mode the camera is also trying to make a
correct exposure but based on its measure of the ambient light as it has
absolutely no knowlege that the flash exists let alone being able to
measure or control it. What you're probably seeing is a "correct" flash
exposure controlled by the flash and a "correct" ambient exposure
controlled by the camera for a grand total of twice as much light as
To regain your exposure composure place the camera in manual mode and
use one of the two apertures as indicated by the auto mode dial on the
T-20's calculator panel. While you may think there are no electical
connections there are. One is a switch at the top left controlled by
whether the calculator panel is inserted or not and the other is the
slide switch at the bottom which informs the flash of the camera's
aperture/ISO combination as set by you on the calculator panel.
After setting the camera's ISO on the flash you choose one of the two
apertures based on the distance range you want to cover or other
aperture selection criteria (such as DOF) assuming it fits with the
available range of the flash at that ISO/aperture combination.
Remember that, with flash photography, there are always two exposures
going on. The first is the flash exposure which is extremely short and
bright. The second is the ambient exposure which you will allow or
disallow according to the manual shutter speed you have selected. If
you choose a high shutter speed in a dark room there will essentially be
no ambient exposure added to the flash exposure. If you choose a long
exposure, say 1/8 second, you may add a signficant amount of ambient
light which may be useful for adding illumination to the background at
distances the flash can't reach or can't reach with the same intensity
as the foreground. This dual exposure control is used in the reverse
sense when doing fill flash. In fill flash, the ambient exposure is the
principal exposure and the flash exposure power is controlled such that
it adds only a fraction of the ambient light level in order to brighten
the shadow areas a bit.
Brian Swale wrote:
> The current issue now is to get the E-1 to make well exposed images. So far
> they are grossly over exposed. The shutter stays open far too long, f/22 at
> 1.5 metres in A mode. Working on that now. P setting is worse.
> Whether the T20 is set on manual or auto makes little change. (Don't see
> how it could, as the panel seems to be merely a sliding-rule kind of
> calculator. I can't see any electrical connection to the flash circuitry)
> If the worst comes to the worst, I will control the issue by using Manual
> mode, and judge the goodness of the exposure from the rear screen picture.
> But that seems to be a clumsy solution. The camera should solve this
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