The official Fujifilm X100/X100S 49 mm adapter ring which allows you to mount extra filters onto your lens will run you about $40, which is a little steep considering that its entire role in life is to act as an expensive spacer.
This X100 review pointed me in the direction of an inexpensive alternative hack that is both cheap and fun. All you’ll need is a single $4 49 mm UV filter, a somewhat heavy metal implement like a hammer, and whichever accessory you actually want to mount on your lens.
First of all, remove the thread cover from the X100s to reveal threading suitable for mounting a filter. The cover is a tiny metal ring right at the outer edge of the lens. You should only have to twist very gently in the counter-clockwise direction to start spinning it off.
Now we can’t simply mount our new filter onto the camera because it will end up too close to the lens. Focusing on a near object will extend the lens enough to hit phyiscally hit the filter, which will shut the camera down. This is where the adapter ring comes in — it spaces the lens out from a mounted accessory enough that it has enough room to move around.
Luckily, we can make our own. Take your cheap UV filter and smash its glass out with a metal object of your choice. I did this inside of a plastic bag to protect myself from dangerous shards of flying glass. Be very careful to make sure that you get all the little pieces of glass from out around the filter’s rim before attempting to mount it.
Now you’re ready to mount the UV filter onto your X100S where your thread cover used to be. You should end up with something like the following.
Your lens now has a bit of breathing room! Whatever accessory you were trying to mount on the X100S in the first place is now ready to be threaded onto your empty UV filter (even if it’s just another UV filter). Optionally, remount the thread cover removed earlier on top of that.
And you’re done! Just as quick, easy, and fun as promised.