VND fog filter with strong effect for the PolarPro BaseCamp Stage 3 filter system. Must be used in conjunction with the circular polarizing filter to utilize the variable stop range. Stop reduction: 2-5. Optical density: 0.6-1.5. Light transmission: 25-3.125%. Diffusion strength: approximately 1/2. Fingerprint-free installation possible. ND filter - extend your exposure time. A neutral density filter (ND filter) or gray filter blocks a portion of the incoming light. With a gray filter, you can significantly extend the exposure time, achieving effects such as blurred water or preventing overexposure in bright sunlight with an open aperture.