This Benro Reverse 0.9 ND filter is a 150x170mm 3 stop reverse gradient neutral density filter with a gradient that fades in two directions. The top of the filter smoothly increases in intensity to provide 3 stops in the middle of the filter. From the middle down the filter fades to clear.
This is ideal for photographing sunsets or sunrises, where you may find yourself shooting towards the sun as it sits near the horizon. A standard gradient filter would darken the sky at the top of the frame, while possibly not darkening the sun enough. With a reverse ND filter it is possible to move the filter up and down in the holder to position the darkest part of the filter over the brightest part of your image, bringing detail back in to this portion of your frame.
This filter is 2mm thick and designed for use with the separately available Benro FH150 Filter Holder, however is usable with most 150mm filter holders. It is possible to stack any number of ND's together with other filters, to customize your Benro filter setup for any lighting situation.