Just got the LX100 and love the camera. A few discoveries when using filters with the camera:
1. The filter size is 43mm, but the lens is 58mm in diameter. I already have several 58mm filters, so I wanted to use a step-up ring.
1. The first 43mm - 58mm step-up ring I tried would bind when the lens fully retracted. I replaced it with the brass Heliopan ring and it worked perfectly.
2. Even at 58mm I would still get some vignetting at the widest angle when adding an Ultra Contrast 3 filter and the ND fader I had.
3. Switching to the 58mm Tiffen ND Fader removed the vignetting because of its 67mm outer ring. It has enough thread to hold a 67mm lens cap.