I found that it was fooling my meter and causing me to actually overexpose the image. I would have thought it would tend to the opposite since you loose a stop of light or two. Anyway long story short I found I got better results by underexposing 1/3 -2/3 of a stop. I shoot in manual so I am very sure about the meter readings. This is the first I have noticed this. I tried both matrix and center weighted with the same results. I am curious as to why the filter would affect the meter in this way.