-----Ursprungligt meddelande-----
Från: John Hermanson <omtech@xxxxxxxxx>
Till: olympus@xxxxxxxxxxxxxxx <olympus@xxxxxxxxxxxxxxx>
Datum: den 24 februari 1998 21:40
Ämne: Re: [OM] OTF in IS-3?
John Hermanson wrote:
>The IS-3 computes exposure through the mirror, reflected to the cell in the
>floor, before the mirror goes up. At this time, exposure info goes into
>memory.
>Flash exposure is based on distance (similar to Olympus Flashmatic used in the
>35RC etc.).
>
>John
>
John, you say the IS-3 does not have OTF flash metering, instead flash exposure
is based on distance like the old Olympus Flashmatic system. I checked the
flash info in my IS-3000 manual and it speaks of "a new exposure control system
that combines the advantages of both flashmatic, used in compact cameras, and
auto flash found in SLR cameras". The difference is said to be that "flashmatic
emits full-strength flash while automatically adjusting the aperture for proper
exposure", while "auto flash varies the amount of light emitted by the flash,
and sets the exposure by measuring reflected light". The manual continues: "The
IS-3000 adjusts both the aperture and flash strength to give you perfect
exposure every time, taking into account the effect of the background light and
the distance to the subject".
It further describes the dual-strobe flash system:
"Olympus developed the dual-strobe flash system with two sets of tubes and a
reflective backing that are ideal for both wide-angle and telephoto
photography. This makes a powerful, versatile flash with GN28 possible.
The lower tube is designed for telephoto photography and offers GN28 ~ 1.4. The
upper tube is an intelligent variable-power flash offering GN20 ~ 1.4. When the
camera-to-subject distance is less than 1.2 m in the Macro mode, the upper
flash will automatically fire to prevent the flash light from being obstructed
by the tip of the lens.The flash is also capable of emitting minimal intensity
for ideal macro photography."
To me this does not sound as if the flash system in IS-3 is identical to the
old Olympus Flashmatic system. Did this adjust both the aperture and flash
strength? My guess is that in telephoto the GN28 flash fires the lower tube
with full output varying the aperture for correct exposure, while in wide-angle
and macro mode it uses the upper tube varying the output as well.
I´ve also been reading the comments from listmembers on the F-280 flash and
it´s weak output when used in super FP (full synchro) mode. The built-in GN28
flash in IS-3(000) also perform full synchro when the camera is used in
portrait or manual mode (with faster shutter speeds), and according to the
aperture/shutter speed setting tables for flashphotography in the manual this
seems to apply to the GN28 flash as well but perhaps not as dramatically. In
ordinary flash photography with ISO 100 film and shutter speed 1/100 s or
slower the range varies from 1.2 ~ 1.5 m at F16 to 3.2 ~ 4 m at F5.6 (range at
F4.5 being omitted), while in flash photography at faster shutter speeds (super
FP emission) the range varies from a maximum of 8 m which can be achieved only
at F4.5 and 1/125 s to a minimum of 1 m at several different aperture/shutter
speed combinations (125/F16, 250/F11, 500/F8, 1000/F5.6 and 2000/F4.5). If we
compare the two manual flash modes at the aperture 5.6 the range is 3.2 ~ 4 m
with a shutter speed of 1/100 s in ordinary flash mode, and 2.8 m with a
shutter speed of 1/125 s in super FP. Of course when there is natural lighting
the camera-to-subject distance increases beyond the above data. Do we have any
comments on this?
Best regards,
Per Nordenberg
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