While no one mentioned Vari. ND, I bought a cheap Vivitar 49mm for my X 70... I have regular ND for my X T1..... And... It's unusable! Only with mirrorless, and at full strength (10x). The EV difference between two corners and the center is over 3EV... I have a friend with an X 70 using a more expensive vari. ND, and it works "pretty" well... My advice: be careful using Vari. filters... I have no issues with fixed ND's.