I have a Nikon D90 with the 18-200mm VR lens. With a UV filter on the lens it is super crisp in focus from 18-200 mm. But when I put a CPL filter on the lens it is very crisp in focus from about 18-100 mm and from 100 mm - 200 mm it won't focus, even in manual. Is this normal, anyone else ever have this problem? Is the filter just a total POS? Its a Crystal Optics filter. Thanks.