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RE: [OM] G28 flash diffuser?

Subject: RE: [OM] G28 flash diffuser?
From: VELUWEH@xxxxxxxxxx
Date: Thu, 26 Nov 1998 05:51:35 -0500
Per Nordenberg wrote:

>Yes I know this. What I meant was how the built-in flash works in the
IS
>system. Some say it works like the old flashmatic system and some say
it
>is a TTL flash system. I know weove been through this once before, but
>correct if Iom wrong but I think in a flashmatic system the flashlight
>may not be disturbed by a diffuser.

AFAIK, the built in IS flash and the G40 flash used in standard mode
use an extended, intelligent flashmatic system that is not only based
on the GN formula but can also dynamically change the GN, which is
accomplished by changing the flash duration. This gives you the same
amount of freedom for aperture setting as a TTL flash system. This is a
great improvement over the simple flashmatic system used in
rangefinders like the Olympus RD or the Canon Canonet, where a fixed GN
must be selected, giving only one (automatically set) aperture for each
distance.
The benefits from a flashmatic system is that it isn't fooled by
extreme reflectance from the subject or the background. The shadowside
is that, like manual GN calculations, in many cases the GN can't be
trusted since it is based on rooms with average reflections from the
wall. One thing you can't do with a flashmatic system is using
diffusers that change the GN (without the camera knowing it), _unless_
you deliberately want to reduce the flash effect (fill-in) _or_ the GN
w/o diffuser was too high anyway. And I think the latter just might be
the case with the built in IS-3000 flash combined with the macro
converter: the distance probably just becomes too short even with
aperture fully stopped down. You can compare this with the usage of the
ND filters for the T32 at short distances.
The second purpose of the diffuser typically will be to bend the light
towards the subject, simulating a bounce head. Without it the lens
probably will be in the way and the flash beam would have a paralax,
not covering the whole subject.
BTW, when you use a diffuser like the Omni Bounce on the G40 you must
tilt the flash head upwards, which sets this flash from flashmatic to
computer flash mode, using its built-in sensor. The reduction in GN
will automatically be compensated by a longer flash duration.

Hans

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