Maven Filters has announced the Iron Slider Gradient Adapter , which it calls “the most flexible way to control your graduated ND filters.” The system combines a magnetic adapter and Maven’s 95mm Graduated ND filters to deliver precise control over graduated filters. The Iron Slider Gradient Adapter is available for 72mm, 77mm, and 82mm filter threads, covering a wide range of very popular lenses. While the interior diameter ranges from 72 to 82 millimeters, the exterior dimension is much wider. It looks like a giant step-up ring. This extra space around the opening allows photographers to freely move a 95mm Maven magnetic filter up and down the front of their lens. Typically, having the ability to control where the gradient is in the image requires using large square or rectangular filters, like these . As Maven Filters notes, these filters are big, bulky, expensive, and take up quite a bit of space in a camera bag.…