Negative Positive
Title: Sharpness, of the lack thereof
Review: I've had this filter since February 2010 and use it on a Nikon D90 with a Sigma 18-250 lens. I've found that it is impossible to get a sharp picture when the lens is at or approaching 250mm. I've taken "identical" shots with and without the polarizer to determine if the problem is the lens or the filter and the filter comes up short. At wide angle to short telephoto the filter seems to do alright, but at long telephoto it produces a fuzzy photo that I cannot get to be "crisp" either with automatic or manual focusing, even when shooting from a tripod and making sure the aperture is the same to ensure the lens isn't the culprit.
Is the review positive or negative? 