There is the case that you carry multiple standard ND filters and choose one of them, or stack them to realize desired ND value at the shooting site. This filter can reduce light intensity over a wide range from 1/2.5 to 1/500. Since the desired ND value can be adjusted by rotating the filter ring, there is no need to carry many ND filters with different densities. Despite of its double frame structure, it employs slim profile frame (thickness is 5.9mm without thread) to prevent vignetting. For adjusting exposure time: The desired shutter speed can be adjusted without changing the aperture. For adjusting aperture: The desired depth of field can be obtained by adjusting aperture without changing the shutter speed.
Multi-coating for low reflections
Satin finished frame
Knurling on the frame for easy operation
Blackened outer rim for reducing inner reflections