In article , duncanm@xxxxxxxxxxxxxxxxxxx writes
>We're all trying to think about this too hard.
>
> The easiest way would be to build an external
>sync-delay circuit, so that the flash is triggered
>some time _after_ the on-camera sync pulse.
>
> Then you just dial in the delay you need
>(1/60, 1/30, 1/15 etc.) depending on the
>selected shutter speed.
>
> Of course, this wouldn't work in auto mode,
>but what do you want for a few bucks?
>(and besides, it would work on all your
>cameras)
>
>
> duncan
>
A brilliant idea Duncan - opens up the possibility of TTL flash with
variable fill ratio on OM cameras! A problem that has dogged the system
for years.
Its easy to increase the ratio of daylight to flash above 1:1 - just
adjust the aperture until the camera meter indicates a slower speed than
the flash sync. At 1/60 and above the fill is around 1:1, so at 1/30
the fill is 2:1 - more flash than daylight. Unfortunately there is not
a lot of call for the ratio to be adjusted this way! What is generally
required is more daylight and less flash, and your gizmo would permit it
by delaying the flash trigger.
Adjust the aperture until the daylight shutter is around 1/30, then set
a delay of 1/60 on your gizmo. By the time the flash is actually
triggered the camera meter will have integrated half the required
exposure from daylight, so the flash will provide the other half, giving
again a 1:1 fill ratio. Now make the delay 1/40th of a second. The
camera meter will have integrated 3/4 of the necessary light from
daylight by the time the flash triggers, so the fill ratio will be 1:4.
Should be relatively simple to get other ratio's by experiment.
Like most good ideas I suspect someone must have thought of it before.
Does anyone know how other variable fill ratio TTL flash systems work?
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
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