: I thought the GN was 28 but am I thinking too simply?
This GN of 28 applies only to Manual Mode and Normal TTL Mode. In FP the GN is
reduced because of the stroboscopic effect (lots of tiny flashes instead of one
big flash) and is shutter speed dependent because the shorter the shutter speed
the less effect is received from all these flashes.
: What shutter speeds to these GNs compare to?
On my e-SIF page for the F280 there are all the graphs and tables from the
manual. In my previous posting I listed the FP GN's in Manual Mode for the
various shutter speeds 1/2000, 1/1000, ..., 1/60sec and above.
: I think I need to book (someone can write it I guess)
: called "OM4T and OM3T Fill Flash for Dummies."
Maybe an idea for the e-SIF pages. Shall I create it in Olympus style, with
pictogrammes? ;)
: This I never did understand totally. So I take it that the OM4T first takes a
: reflected light averaging reading, spot reading or spot averaging reading,
: then FP flash fires on the closed shutter curtain to determine the shutter
: speed, adds it to the previously reflected light reading, and then calculates
: the shutter speed according to some internal formula that nobody knows??
Much simpler than that. First, spot reading doesn't work together with flash, FP
or not. Second, it works just like normal averaged TTL mode with available
light, when right during pressing the shutter release button an additional light
source is put on (like when a cloud disappears an the sun 'begins to shine'):
the OM-4Ti automatically responds by selecting a shorter shutter speed than
originally was indicated in the viewfinder. So all it really does is firing the
F280, and measuring how much light is read from the curtain, no matter where
that light came from: mainly flash, or mainly available light, or a balanced
mixture. For this reason you always get a flash ok signal in FP mode: exposure
is always ok even if the actual effect of the flash was zero because the subject
was too far away.
: Also why does the Manual B for OM4t say that Super FP duration is 20 to 40
: milliseconds? What does this variable depend on?
I'm not sure how you associate 'Manual B on the OM-4Ti' with the flash duration,
but the manual for the F280 says that the flash duration in FP mode varies from
1/50 to 1/25 sec with the OM-4Ti and OM-3Ti, and from 1/70 to 1/30 sec with the
OM-707. I've never seen the real explanation, but at least the speed difference
between the cameras must have something to do with the speed of the curtains
(the OM-707 has a faster curtain). And I can only guess that the slower speed
(1/25) is used when the camera is set to manual, with shutter speeds of 1/30 or
longer. Interesting point is that allthough the flash is synchronized from 1
sec. to 1/2000, with the longer shutter speeds the flash only emits light during
a portion/fraction of the total exposure, so does not entirely give the same
effect as long available light exposures...
H@nz
P.S. 1. SUV content: none! This is _still_ the Olympus Mailing List, you know!
(where have I read this before?)
P.S. 2. I don't even know what SUV stands for, because I deleted all the
off-topic shit messages.
P.S. 3. I want to keep it that way, so don't tell me.
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