Olympus never differentiated the OM-2 curtains with the original pattern
and the later pattern with a separate part number - once stock of the
old style curtains were used up, the new type curtains were installed as
needed during repairs without qualm. In other words, they were used
interchangeably.
Also, there was no change in the main circuit - no different part
number. The SBC's on the circuit were the same by all appearances,
whichever style curtain was installed.
What prompted the alteration of the "random pattern" was never explained
- but I would suspect that it was because, (a) the effect on the
exposure was so minute that the "center weighted" pattern was deemed
unnecessary, and (b) the "average" pattern was cheaper to make. 8^)
Chip Stratton wrote:
>
> This is quite plausible, but it may also be that they replaced the silicon
> cell sensor with one whose 'field of view' was more centrally focused, thus
> a center-weighting to the actual curtain pattern was no longer necessary to
> give center-weighted metering.
>
> They did continue to advertise center-weighted metering even after the
> switch, didn't they?
>
> Chip Stratton
> cstrat@xxxxxxxxx
>
> > I can't think of any other reason other than Olympus decided that
> > the majority of photographs were better served by the 2nd,
> > less-center-weighted metering pattern. It also may have produced
> > a better match between the OTF metering (via the shutter curtain
> > pattern), and the in-finder metering.
> >
>
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