Results will be the same with other ASAs because moving the asa is
purely mechanical (cam) and does not change anything electrical.
Also, I found that at BV6 (which is quite dark), room light entering the
eyepiece and around the front of the lens will effect the reading. So,
I covered the camera (and space where the lens touches the light box)
with a piece of dark cloth. I waited a minute or so and carefully
peeked through a corner of the eyepiece. Most, if not all, of that +
1/4 error had disappeared.
John
Frank van Lindert wrote:
>
> On Tue, 20 Apr 1999 17:15:07 -0400, John Hermanson <omtech@xxxxxxxxx>
> wrote:
>
> >Some recent posts questioned the accuracy of the OM-1 with either an MR9
> >or other meter mod. I've compared the meter accuracy of the last 6
> >OM-1/1Ns that I've converted to the silver oxide 357 battery (using the
> >1N34A diode.) Here is what I found:
> >Meter setting is first made at BV12, then the other levels are checked.
> >
> >BV15 = 1/1000 @ f5.6 (asa 100) error = 0 stops
> >BV12 = 1/125 @ f5.6 (asa 100) error = 0 stops
> >BV9 = 1/15 @ f5.6 (asa 100) error = 0 stops
> >BV6 = 1/2 sec @ f5.6 (asa 100)error = +1/4 stop.
> >
> >All 6 cameras were identical, once the meter was set up at BV12.
> >
> >John
>
> Thanks, John this is valuable information!
>
> Do you think that the BV comparison with fixed aperture and film
> sensitivity allows for the conclusion that the meter with diode
> modification is doing very well in almost all light situations?
>
> Or could the results be less perfect with other film or other
> apertures?
>
> I hope that I will be able to reproduce your modification, since it is
> not practical to send my cameras to and fro across the Atlantic for
> this...
>
> I would do it this way:
> 0. check the meter without the diode, and calibrate
> 1. put the diode in, in series with the battery
> 2. trim the 'new' meter at 1/125 @ f5.6 (ISO 100)
> 3. check at higher/lower BV values.
>
> Is that about your way of doing it?
>
> Thanks,
>
> Frank.
>
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