i have used the hoya fld filter on my a100 and on my 300 its a 52mm version & it screws directly onto the inner ring of the lens, i havent used the filter much with my 300 though as i feel the picture is better without it , ( i used it all the time with my 100 as the VB was bad on that) my 300 isnt to bad with the VB and i am happy with the blacks, i fell the filter makes the image to dark for my taste so i dont use the filter.