Originally posted by polar bear This only happens with the HD 16-85, about one overexposed picture in a hundred correctly exposed pictures. This has never happened before with my Pentax 18-135mm WR, my Pentax 100mm WR and my Sigma 10-20 4-5.6.
... and I haven't heard of it happening before with the 16-85 either (though I do get something similar with the Sigma 35mm Art, rather more often than 1 in 100).
But your case is not just inaccurate metering: both your original photos have the same aperture, iso, and exposure time in EXIF, which CAN'T be right! So there is a miscommunication of some sort.