I have three 77mm Variable ND filter now. Tiffen 77mm Variable Neutral Density Filter-$150, purchased at b&h FOTGA 77mm Slim Fader Variable ND filter-$15, purchased at ebay.com Nature 77mm Variable ND filter MKII- around $80 (converted from Chinese dollars), purchased at China, This is the most expensive Chinese made Variable ND filter I find at China. However I…