I just got my MC Rokkor 50mm f/1.7 today and took some test shots with my PL1. However, the camera didn't seem to meter properly with either ESP or center weighted metering. Example: Lens @ f/1.7, camera meters 1/20 sec at ISO 200 Lens @ f/2.8, camera meters 1/12 sec at ISO 200 Lens @ f/4, camera meters 1/18 sec at ISO 200 Is there a reason why the camera isn't metering properly? f/2.8 is about 1.4 stops slower than 1.7, so the camera should have metered something like 1/8 sec instead of 1/15.
ESP won't give correct readings for lenses without electrical contacts. I assume you have set the camera to Aperture Priority. Centre weighted should work OK at those sorts of light level, try spot metering and see it that helps.
