The hitech 100x150mm nd reverse graduated 09 filter offers the transition from dark to light from the middle of the filter upwards ie in the reverse of a standard nd grad filter dark to light from top to middle this is a benefit when shooting bright horizons to enable more control over the exposure and balance the foreground image the nd graduated filters are clear in the bottom half with a gradual transition to the nd effect in the top half of the filter they produce a grey neutral tone a