All our filters are carefully formulated to ensure consistent color and accuracy throughout the entire surface of the glass. Why? Consistent color means consistent high quality results. We know that a poorly made filter makes a great lens and camera worthless, that's why the our frame rings are constructed of special alloys that won't expand or contract over time or due to temperature extremes-it's also why we back our filters with an 10 year warranty-because we engineer them to last.