9xi Metering

Now I have discovered this site perhaps one of you can help.

When using my 9xi with any Minolta AF lens it seems as though it

under-exposes when in portrait (vertical) format. Using landscape

(horizontal)exposure is deadly accurate as expected. It is more

noticeable when using the 20mm lens. This bugs me because I see

better vertically than horizontally.

I use Program mode nearly all the time. Using spot metering is fine

whatever the orientation.

Is this a foible of the 9xi and can others duplicate this?

Rod