Graduated Neutral Density Filter, also called as Grad ND filter is one which has got two halves. The first half of this filter will be a neutral density one and the second half will be a clear section.  The main purpose of such a filter is to overlay the bright part of the picture scene into the dynamic range of the sensor. It is one of the favorite filters of Landscape photographers. Graduated Neutral Density Filter is mainly used to correctly expose the brighter part of the picture scene, especially the sky. Thus helps to expose picture correctly. They are available in different shapes and sizes. 

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