A couple of days ago the camera started doing some odd things. It was under exposing by three stops with the ND filter off and between five and six with it on. I noticed it when out of the blue, the camera suddenly selected around 1/60 sec in AE for a scene in open full sun at f16 when I was using an effective ISO of 400! (3200 with ND engaged) I turned the ND filter off, selected ISO 400 and took a photo in full sun at f16 and manually selected 1/500 shutter speed and got the same result ... very under exposed! I did a reset to return the camera to factory defaults and tried again and got exactly the same result. If I manually set the shutter speed three stops slower than what the light was telling me it was fine ... perfect exposure in fact! The interesting thing is that in AE the camera's metering is compensating for whatever is going on and giving a decent exposure but at a three stop slower shutter speed than it should ... so the problem is obviously ISO related and will have something to do with the ND filtering software for sure.