Linear Rotating Polarizer (with locking screw).
Used to eliminate glare, a linear polarizer in a rotating mount offers flexibility and ease of use. Once the filter is screwed to the lens, the outer portion of the mount rotates freely. This facilitates determining the point where reduction of glare (or the contrast in stress patterns in glass or plastic materials) is maximized. However, because the mount rotates freely, it is also possible for vibration or other inadvertent interference to cause the filter to move from this position and adversely effect the system's performance. For this reason, all MidOpt polarizers come with a locking thumbscrew to insure that jarring or accidental movement during cleaning does not result in a change in the filter's position.