Reviews: Vivitar 72mm Variable ND Filter - 0.3 to 3.0 (1 to 10 stops) VIV-VNDX-72
FZ1000 and variable ND filter: Panasonic Compact Camera Talk Forum: Digital Photography Review
Nd Filter Fader Neutral Density Adjustable Nd2 To Nd400 Variable Filter 37/46/49/52/58/62/67/72/77/82mm For Nikon Canon Camera - Camera Filters - AliExpress
Fstoppers Reviews The Singh-Ray Variable Neutral Density Filter: A Must For Any Landscape Photographer | Fstoppers
55mm Variable Nd Filter Nd2-1000 , 10 Levels Adjustable From Nd2 To Nd1000, For Lenses With 55mm Filter Thread - Camera Filters - AliExpress