The 150x170mm Reverse Nano IR Graduated Neutral Density filter – ND8 (0.9) – 3 Stop is a rectangular filter that helps to darken specific areas of an image, such as bright skies while allowing for a normal, unaffected exposure in the other regions of the image. Reverse edged GNDs are similar to hard-edged GNDs except that the darkest part of the filter is at the transition point. These filters have a specific use for shooting at the light source where the light is harshest at the horizon and tapers off toward the sky. This type of filter is most appropriate for scenes which have a sudden transition from the foreground to the sky with the brightest part of the scene near the horizon. Most commonly, this would include landscapes with no elements protruding above the horizon such as a seascape looking toward the open ocean. They can be used shooting into the direct light where a sharp transition is needed.
NiSi GND filters do not affect the coloration of the image, offer a true to life color and are made from high-quality optical glass (not resin) with nano coating to prevent losing any single bit of detail. By using neutral density filter the camera is vulnerable to infrared light which will cast the unwanted red color to the photos when shooting at a small aperture. NiSi GND filters have an infrared protection coating layer to eliminate the infrared light through the lens to bring back the natural true to life color.
The NiSi 150mm filter system is great for cameras with lenses that do not have a standard filter thread.