The Schneider Optics 68-884407 77mm Landscape Variable Neutral Density Upgrade Kit is used for the Schneider Landscape Control Kit, which allows you to create a Variable Neutral Density Filter.
This carefully matched set of filters works in combination to produce a density range from 1-1/3 stop loss to 11 stops of light loss. By selecting the best quality materials, Schneider variable ND filters offer 11 stop (ND3.3) attenuation with no blue color shift at maximum density.
The kit includes a screw-on 77mm True-Match Circular Polarizer (Non-Rotating) filter that mounts to the front of the camera lens and a 4 x 4 True-Match Linear Polarizer.
Note: An anomaly may occur when using a Variable ND filter when shooting wide angle (50mm and below) near to or at the highest ND point on the filter. The anomaly can be a very dark area in the center of the image, or an "X" pattern with lighter frame edges.