We took our industry leading X4 ND filter and applied the same proven technology to the graduated neutral density filter, manufactured it with tempered SCHOTT B270® optical glass made in Germany, and the result is the X4 GND – the world’s sharpest and most color neutral GND, guaranteed.

Legendary landscape photographer Galen Rowell developed the GND filter with Bob Singh of Singh-Ray filters, and together they pioneered a method for covering the dynamic range gap of 35mm film.

Singh-Ray’s line of American-made GND filters have been the industry leader for decades, delivering unparalleled color neutrality. Singh-Ray’s use of high quality CR-39 optical resin also provided unparalleled resolving power.

The X4 GND introduces a new era of durability and resolving power by using SCHOTT B270® optical glass, made in Germany, and it’s the world’s first tempered glass GND. The result is an incredibly durable filter glass that doesn’t break even when dropped onto hard surfaces.

Another benefit is that the optical surface does not degrade over time or with exposure with corrosive elements such as salt water and sand, common conditions for outdoor photographers.

The X4 GNDs impressive structural hardness also prevents warping, a common issue that develops over time with traditional resin filters, especially when not stored flat. Slightly warped GNDs can add slight distortion noticeable on wide-angle full-frame setup.

Traditional CR-39 resin had exceptional sharpness performance if the surface was in mint condition, however CR-39 proved to be a poor material for accepting coatings, and therefore the industry leading CR-39 GNDs by Singh-Ray and Lee are without MRC or nano coatings.

Each X4 GND has our state-of-the-art MRC16 and nanotec coatings technology applied to both sides of the optical surface. This reduces surface reflection and nano coatings make handling and cleaning the surface of the glass easy. The nanotec coatings also let the X4 GND glide smoothly in the holder.

The edges of each X4 GND are then milled down smooth, and an outer-layer of protective coating is applied along the edge of the glass.

The X4 GND features SCHOTT Superwhite B270® optical glass, which is an ultra clear crown glass. It is produced by melting high purity raw materials and then made using the continuous draw process. The result is excellent transmission in the ultraviolet, visible, and infrared spectrums, and a high surface quality that accepts our state-of-the-art MRC and nanotec® coatings exceptionally well.

Our state-of-the-art multi-resistant coating (MRC) is an optical coating applied to both surfaces of the glass disk to reduce reflection and to increase surface durability. Our proprietary MRC coating is structurally harder than the glass itself and the reduced reflections improve the efficiency since less light is lost. The reduction of reflections also improves the contrast of the image by elimination of stray light. The real world result? Better contrast and color.

Low light transmission and green flaring are common problems with uncoated glass. As MRC coatings are added to each side of the optical disk light transmission steadily increases with flaring steadily decreasing. In our lab tests light transmission apexes at about 16-layers of MRC, and slowly decreasing in transmission at 18 and above. 8-layers of MRC are applied evenly to both sides of each optical disk resulting in MRC16.