Inaccurate metering at slower shutter speeds w/ MF lenses?

Hi,

I just noticed that my E-P1 does not seem to expose properly with MF lenses when the shutter speed is less that 1/15 or so. I noticed this when testing two lenses and it's the same with both.

I set up a tripod and took sequential pictures with each lens. Camera set on aperture priority. Starting at f2.8, I opened the aperture a full stop (2.8, 4, 5.6, etc) with each picture. The starting shutter speed was about 1/13 at ISO 400, then 1/10, then 1/6, etc. I believe the shutter speed should have been cut in half each time, shouldn't it? In any case, the pictures were indeed progressively underexposed.

This does not occur with AF lenses.

Can anyone explain this?

Thanks,
Tom

 

Seems to be more about shutter speed for me...

Peter,

Interesting observation. For me the phenomenon seems to be more shutter speed related, eg, using a 40mm lens (80 equiv), I'm seeing it at 5.6 and 8 - not usually considered small aperture levels. At higher light levels, I get good exposures right up to f11 (haven't tried higher).

Will continue to experiment...looks like changing from ESP metering to center weighted fixes the issue??

Best,
Tom

 

Peter,

Your note confirms what I had noticed: center weighted seems less sensitive to the issue. It would be nice to understand the 'why', but in the meantime, we have a decent solution.

Best,
Tom