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[OM] metering with an OM4T

Subject: [OM] metering with an OM4T
From: "John Hudson" <13874@xxxxxxxxxx>
Date: Tue, 30 Sep 2003 12:01:29 -0300
Perhaps other list members have experienced what I describe below and might be 
able to offer some useful comments and opinions. 

My OM4T has just been returned by the Canadian Olympus service / repair 
facility in Toronto after a thorough CLA and shakedown. I have been assured 
that shutter speeds have been calibrated to Olympus standards, etc, etc.

I am confused as to the accuracy of the shutter speeds or at least the shutter 
speeds I see through the viewfinder. Before being sent in for service there was 
always a very close approximation between incident light readings taken with my 
Sekonic L508, spot readings taken off a gray card with the same meter, spot 
readings taken with the OM4T off the same gray card, and the average reading 
after taking several multi-spot readings with the OM4T through the viewfinder 
so as to approximate 18% middle gray. Almost invariably the approximation was 
within half a stop or less and as a final check it invariably accorded with the 
"sunny 16" rule given the state of the ambient light.

Since the camera has been serviced, the meter readings in the viewfinder, 
whether the average of several multi-spot readings or in auto mode, are showing 
generally one and half stops over exposure as compared to readings with my 
Sekonic whether off a gray card or in incident mode. This is disturbing and 
doubly so since I shoot mainly slide film where the exposure latitude is less 
than plus / minus half a stop.

I have just collected seven rolls of slide film [Ektachrome E100GX and Provia 
100F]  from a professional lab wherein I exposed numerous duplicates using the 
OM4T's multi-spot metering function alone and then setting the camera to manual 
and using the exposure shown by my Sekonic in incident mode. In all those cases 
the incident readings set on camera were the same one and a half stops under 
exposed as compared to the camera's measurements as seen in the viewfinder. 

I now find myself in the odd position of discovering that the multi-spot 
metered exposures are virtually perfect whereas the manually set exposures 
based on the Sekonic's incident reading are between one and two stops under 
exposed. 

The Sekonic's incident readings along with its spot meter reading off a gray 
card  are virtually identical [ + / - 1/3 stop] and accorded with the sunny 16 
rule so I feel comfortable that the Sekonic is accurate. As a further check on 
this meter's accuracy I have a roll of Provia 100F shot in a Leica M3 using  
90/2.8 and 50/2 lenses where I used the Sekonic's incident reading in all 
cases. Those slides are properly exposed to within + / - 1/4 stop or so my eyes 
judge.

Thus, I am left with a hand held meter that by all accounts is accurate and TTL 
metering in my OM4T that shows ~ 1 1/2 stops over exposure in the viewfinder as 
compared to the Sekonic and yet produces ideally exposed slides! For all seven 
rolls of film I made doubly certain that the plus / minus exposure compensation 
dial was set to zero and that the film speed was correctly set on the ISO dial. 
Where I used a circular polarizer I increased the Sekonic's indicated exposure 
by 1 1/3 stops. Again, I was still having the camera TTL meter showing me to be 
1 1/2 under exposed.

As for lenses used, the great majority were taken with a 35-80 / 2.8 Zuiko 
zoom, and the others with 24 / 2.8 and 85 / 2 Zuikos. There is no evidence to 
suggest that the indicated aperture on any lens is inaccurate. The under / over 
exposure issue prevails regardless of lens used. 

Any and all opinions and comments will be greatly appreciated. I am in the 
position of having to ditch my Sekonic so as to get perfect exposures with my 
OM4T knowing that the indicated exposures in the viewfinder are seemingly 
incorrect, and yet keeping it close at hand if I use my old rangefinder!

John Hudson
     
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