The Schneider Optics 138mm Drop-In Circular True-Pola Filter is a "Circular" True-Pol for Video Assist. Schneider offers a circular True-Pol Polarizing filter for cameras which use polarizing elements in the beam-splitters of the viewing system, such as ARRI 435 and the Movie-Cam Compact. Beam splitters send light in two directions: to an eye-piece and to a video tap. Light in a cameraﾒs viewing system can become polarized, and when a standard (linear) polarizing filter is attached to the lens, the light becomes cross polarized. This hinders visibility and may create total black-out of the viewing image and/or the video tap. Schneider Circular Polarizers feature a two layer design to prevent this blackout. The first layer is made up of the same polarizing material used in all True-Pol filters; the second layer is a 1/4- wave retarder plate which effectively prevents cross-polarization. To ensure correct placement on the lens barrel Schneider clearly marks the outer surface on all Schneider Circular True-Pol Polarizing filters. Note: Circular polarizers are specifically designed for use with auto-focus SLR cameras (They will also work on manual systems and video cameras without problems) Reduce glare and unwanted reflections Saturate colors Deepen blue skies Improve contrast Penetrate haze True-Pol Polarizing filters enable you to achieve a level of optical performance previously unavailable to cinematographers