Model S9DF14. Series 9 size (unthreaded drop-in style) intended for a Series 9 compatible adapter, retaining ring or shade. Lenses in the 62-85mm range are generally appropriate for Series 9 use. The Tiffen Series 9 Double Fog 1/4 Filter simulates the effects of natural fog or mist by creating a soft glow around highlights and lowering the overall contrast of the scene.