I have not purchase a filter kit for my camera. Sony does sell a snap-on filter kit which costs RM 99.00. Thought of getting that but since I think I will only use it occasionally, I put the purchase on hold.
Without a proper filter kit, what did I do? Handheld filter of course! I put the camera on tripod and held the filter in front of the lens. I borrowed the ND10 filter. The RX100 however only allows aperture up to f11.
f11, 10 sec, iso 100
f10, 8 sec, iso 100
f8, 10 sec, 1/1125
f8, 10 sec, iso200
Played around with the filter and got multiple-exposure alike!