When using cameras with video assist and modern beam splitters, it is necessary to use special polarizing filters called "circular polar filters". The term circular does not mean they are round but rather refers to technology used to make them. If these circular polar filters aren't used, there will be problems with either image in the finder or on the video assist. The image on the film will be OK. The reason for this is that modern beam splitters use a dielectric coating that has polarizing tendencies and since two polarizing filters can not be used together, there will be problems. The circular pola filter has a front and back. The front must point towards the subject or it won't be effective.

The 16SR-3 viewfinder gets a magenta appearance with ordinary pola filters. On other cameras, the video goes very dark. This does not happen with circular polars. If you own an auto-focus still camera or an auto-focus video camera, it also needs circular polar filters to work properly. Three chip video cameras also need circular polar filter.