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Re: [OM] T20/T32 Question

Subject: Re: [OM] T20/T32 Question
From: VELUWEH@xxxxxxxxxx
Date: Tue, 25 Aug 1998 05:12:31 -0400
>I would still imagine that if you were set to manual 16 you would have
>only the reduced power available? Also, if set to the normal auto modes
>I think you would see the behavior described whether the camera
quenched
>the flash or the internal sensor did. It may just get shut off by
>whichever sensor (flash or camera) decides first that there's enough
>exposure.
>Correct. So you can reduce the flash output on TTL auto by two stops
>without the ND filter kit.

Two simple tests can check these assumptions. I did them yesterday.

First of all, does the Camera Auto/Flash Normal Auto combi indeed use
two sensors? Like two captains on the bridge ("This way!" -  "No that
way!")? You can check if the camera sensor (TTL/OTF) is active by
putting on a lens cap. In TTL mode this gives a full flash discharge
and no flash ok. You can check if the computer flash sensor is active
by putting a finger in front of the "O" of Olympus on the flash. In
Normal Auto mode this also gives a full flash discharge and no flash
ok.
So how reacts the weird Camera Auto/Flash Normal Auto to this? The lens
cap attached gives a full flash discharge, and no flash ok. The finger
on the flash sensor gives flash ok. Conclusion: only TTL/OTF. That's
what I thought.
(I performed these tests with camera on tripod, dial set at 100 ASA, a
constant aperture of F8, where both standard TTL/OTF flash and standard
Normal Auto flash 100 ASA/F8 with camera at manual indicated flash ok.
Used an OM-4 and OM-2n).

The second assumption, that Camera Auto/Flash Manual GN 16 yields less
flash power can also be tested. A shooting distance of a couple of
meters, aperture fully closed, camera at Auto and flash at Manual GN
32. Full discharge and underexposure. Now open the aperture stop by
stop untill the flash ok just starts to blink. With this aperture, set
the flash at Manual GN 16. What happens? No difference, flash still ok.
This is also what I guessed. The only way I think the flash can
regulate flash power is by cutting it off. The emitted energy/second
remains constant . This happens both in TTL and in Normal Auto mode.
1/1000 sec. is full discharge (also used in Manual 32, camera manual),
1/40000 sec. is minimum output. So Manual 16, camera manual will be
somewhere (halfway?) between, but Manual 16, camera Auto is TTL/OTF
where the camera can select any intermediate flash duration, w/o any
limit.

BTW, these tests revealed a strange OM-4/OM-4Ti bug. On both my OM-4
and OM-4Ti the flash ok led in the viewfinder did *not* blink in Normal
Auto flash mode, camera manual, while the led on the flash *did* blink.
My OM-2n and OM-3 do give viewfinder led confirmation. Tried it with
two T32 flashes to check the failure was in the camera and not in the
flash.
Another weird thing I already knew is that my T18 flash always
indicates flash underexposure on my OM-4 (but not on my OM-2n and I
think also not on the OM-4Ti), no matter what aperture and shooting
distance, while the  led on the flash blinks in the expected flash
range. So it seems the led on a T flash is more reliable than the led
in the OM-4(Ti) viewfinder. Argh.

Hope they will improve this on the OM-5Ti :-). (The hour is neigh; the
Photokina is just in a couple of weeks and several firms have already
revealed their new products. A 35 mm Hasselblad. Hmm. Olympus anounced
a new P&S. Argh.)

Hans

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