Exposure metering discrepancy between modes

My Canon T90 has a 1/2 stop discrepancy between spot and center weighted metering modes.

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With the entire field of view on a flat and constant illumination blank wall, the spot meter reading will result in 1/2 stop more light (e.g. 1/15 @ f/4) than the center weighted reading (e.g. 1/15 @ f/4.5).

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This doesn't seem right to me. Can anyone confirm/deny this as normal operation?

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Thanks!

I think you can't be sure the difference is exactly 1/2 stops.

It might be a bit more or less but large enough (maybe 1/10 stops)

to make the camera display different values. You could try by

adjusting slightly (less than 1/2 stops) the light intensity.

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I believe there is some adjustments for spotmeter mode but I'm not

sure. I have the T90 repair manual but can't reach it right now.

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I don't have T90 any more, anyone interested in service manual

reprint (the one I have)? I also have focusing screens A and D,

anyone interested?

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Vesa-Pekka