The adaptor ring is crucial to the LEE Filters system. It screws onto the camera’s lens and, in turn, the filter holder clips onto the adaptor ring.
The standard adaptor ring is suitable for use with lenses up to a moderate wideangle. It sits in front of the lens’s front thread. The standard adaptor ring is compatible with all lens focal lengths from approximately 24-28mm (35mm SLR equivalent) and upwards.