Also, the spot meter may need adjustment.
_________________________________
John Hermanson www.zuiko.com
Camtech, Olympus Sales & Service since 1977
21 South Lane, Huntington NY 11743-4714
631-424-2121 For Free Olympus manuals,
please call 1-800-221-3000
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----- Original Message -----
From: "Winsor Crosby" <wincros@xxxxxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Thursday, January 16, 2003 3:39 PM
Subject: Re: [OM] advice needed: SPOT meter reading differs from AUTO on
gray card??
> >Hello Ladies and Gentlemen,
> >
> >a Happy not so New anymore Year to all of you.
> >
> >By chance I noticed something with my OM4 (focussing screen 2-4)
> >which puzzles me: I took a reading from gray card in AUTO (center
> >weighted average), then pressed the SPOT button, and the little
> >diamond jumped one full Stop to the right (double exposure time).
> >The compensation dial was set to Null.
> >
> >I did some more testing: This happens mainly/only with the 21f3.5 and
> >24f2.8, but not with the 28f2 or 50f1.8 (this selection is based on
> >lens availabilty). I also tried my OM4Ti/2-13 focussing screen with
> >these lenses and with all of them there was no difference between
> >center-weighted and spot reading. And with both cameras and with all
> >the lenses the center-weighted AUTO reading was identical and precise.
> >
> >Does anyone have an idea what is going on? Does the combination of
> >2-4 focussing screen and very wide lenses cause this difference? Is
> >there something wrong with my camera?
> >
> >I would appreciate your input!!!
> >
> >Thanks and best wishes,
> >
> >Thomas
> >--
>
> The focusing screen does not have anything to do with the metering in
> the OM4. The light being measured is passing directly through the
> mirror and being reflected down by the secondary mirror toward the
> sensor in the bottom of the mirror box.
>
> If you found variations that disappeared by changing screens your
> methods are suspect. I think that if you carefully recheck the
> variation will have disappeared. Uniform illumination of the field
> is necessary to make this kind of comparison which is hard to do with
> a gray card. It would have to be very large to fill the field of a
> 21 mm lens and still be in focus. I would suggest that you use a
> uniformly lit wall.
> --
> Winsor Crosby
> Long Beach, California
>
>
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