Protects the front element of a lens from vdust, dirt, moisture and potential scratches and provide basic reduction of ultraviolet light and help eliminate bluish cast of daylight.
Graduated Grey Filter
Graduated Grey Filter is an optical filter that has a variable light transmission. It is used to bring an overly-bright part of a scene into the dynamic range of film or sensor. For example, it can be used to darken a bright sky so that both the sky and subject can be properly exposed.
Neutral Density (ND) Filter
Reduces the amount of light entering the lens, thus decreasing camera shutter speed. Useful for situations where motion blur needs to be created (rivers, waterfalls, moving people) or large apertures must be used with flash to avoid overexposure.