The mounted Schneider 4.5" Round 1/4 Wave Retarder Filter is a polarization control filter that is designed for 3D cinematography. The process of recording 3D video employs a reflected image from the silvered surface of a 3D rig's beamsplitter. In instances where the recorded image contains glare, partial polarization can occur as the light entering the 3D rig is reflected from the silvered surface. This can result in disparity between the left and right optical paths created in part by the beamsplitter, and ultimately, a compromised 3D effect.

When this Schneider 1/4 Wave Retarder Filter is used with a 3D rig, partial polarization from the beamsplitter is prevented, helping to ensure that the left and right optical paths have identical properties for a consistent 3D effect with no reduction in resolution.