Photorepublik's 100mm ND filters are designed for larger "Z-series" filter holder systems. Reverse graduated neutral density filters reduce the exposure of the sky, weighted more heavily toward the horizon, fading out towards the top of the filter, perfect for photographing bright sunrises and sunsets. Not only does this preserve the detail in your skies, but it also means you'll spend less time on corrections in post-production. Because these filters are neutral, they will not affect the colour of your image like some other filters. This filter blocks 3 stops of light.