: Hans ............. is this to imply that the F280 takes daylight into
: account as a continuing source of light and opposed to it [the F280]
: reacting to the intensity of the daylight at the instant it [the F280]
: fires? If the former I can understand that the sudden impulse of light
: from the Vivitar might cause a problem but if the latter surely isn't
: the impulse of light from the Vivitar's flash just another source of
: directional light the F280 has to account for when "doing its thing"?
Well compare the situation with a multi flash setup with all T flashes connected
with T cords and a body which supports OTF flash. This works because the
combined flash output + available light (when applicable) is measured, and when
enough light has reached the film all flashes are quenched simultaneously.
In the case of one dedicated OTF flash and one none dedicated slave unit the
F280 will be quenched when enough light has reached the film but the slave unit
will not. So if the F280 is quenched after 1/40.000 sec and the Vivitar does a
full dump at, say, 1/1000 the picture can be (and probably will be) overexposed.
The difference with OTF measuring of flash output and daylight is that the
influence of daylight is measured from the beginning the first curtain starts to
move. First it is measured from the curtain, then from the film. When the first
curtain is 'arrived' and the intensity of the daylight allowed a shutter speed
of 1/60 or longer the flash(es) fire(s) and its (theirs) output is added to the
light already measured; when enough light has reached the film the flash(es) is
(are) quenched. Except any non-dedicated flash that will ruin the carefully
built-up OTF metering...
hnz
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