The bw 77mm 064x 102 neutral density filter reduces the light by two f stops log density 06 and is the most popular nd filter in photographic work it offers many benefits for instance f4 instead of f8 for selective sharpness instead of a great depth of field or 115 s instead of 160 s for a flowing and blurred water instead of a frozen waterfall it has excellent colour neutrality and is recommended as part of a basic outfit