At a factory set combination of asa-distance the camera switches between top
flash tube (low power) and bottom flash tube (higher power.) There is no otf
flash control or cell to read flash exposure as in a regular auto flash
(thyristor).
The IS-3 will set f stop with flash based on distance but also which flash tube
is going off., but that is the only control it has.
John
Camtech
Per Nordenberg wrote:
> 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 i!
> !
> s 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?
>
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