Sigma  DG 52mm Wide Multi-Coated Circular Polarizer Filter
Designed for use with autofocus and multifocus SLR cameras, the Sigma 52mm circular polarizing filter cuts the glare from water and nonmetallic surfaces, letting you enjoy crisper, clearer images. A circular polarizer is intended to improve color saturation and contrast, performing such tasks as darkening the sky in color photography without affecting the color balance. The filter's multilayer coating, meanwhile, optimizes protection for the lens while further reducing reflection. The filter--which is designed to especially benefit wide-angle lenses without vignetting--fits lenses with 58mm filter threads. Note that the polarizing filter does not have a thread on the front filter ring.