Richard Schaetzl wrote:
>
> William Sommerwerck wrote:
>
> > The question this raises is just how the camera can provide accurate
> > (ingnoring reciprocity failure) four-MINUTE exposures in OTF mode. Does
> > the OTF mode use a much-higher-quality photo diode?
>
> It´s the same SBC.
>
> > Or is there
> > something else about the design of the camera that negates the problem
> > of the dark current?
>
> No mirrors?
>
> The OM-4 manual states an lowest EV of 0 for spot metering (with mirror) and
> of EV -5 for OTF metering (exclusive mirror) at ASA100.
Yes, and experience bears this out. You must use OTF for the long
exposures. Spot mode won't go much past a few seconds.
George
>
> Translated to AS1600 it is EV4 (spot) and EV-1 (OTF),
> for ASA3200, EV5 (spot) and EV0 (OTF).
>
> Equivalent of f/1.4 and 1/8s at ASA1600, f/1.4 and 1/15s at ASA3200 in
> spot mode and f/1.4 and 4s at ASA1600, f/1.4 and 2s at ASA3200 in OTF.
>
> Regards
>
> Richard
>
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