The Formatt 4 x 4" Reverse Graduated Neutral Density (ND) 0.9 filter is a unique filter that allows you to photograph sunrises and sunsets whilst retaining foreground detail. Traditional graduated neutral density filters filter from the top of the filter downwards and allow you to balance a bright, contrasty sky with a dark foreground. However, this innovative filter works in reverse. The transition starts in the middle and works upwards, allowing you to control the light where it is brightest (at the horizon) whilst retaining foreground detail. Formatt, a company with three generations of experience in manufacturing professional filters, produces each filter to the highest technical standards. The finest materials, combined with cutting-edge production technology, have resulted in a level of optical excellence unmatched elsewhere. Neutral density filters have four main uses - To enable the use of slow shutter speeds, particularly with high ISOs, to record movement of subjects such as waterfalls, clouds or cars - To decrease depth of field by allowing the use of wider apertures, which helps separate subjects from their background - To reduce the effective ISO of high-speed films (above 400 ISO) and allow their use outdoors in bright situations - To enable cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes that could cause overexposure