I have a telephoto/wide angle set for Petri rangefinder cameras that I have tried with my x100. I orginally bought it for the optical viewfinder that came in the set. I believe there is a similar (perhaps identical re-brand) set for Yashica rangefinders. Each converter is ~1.3x, so we're looking at around 45mm and 28mm equivalent. One nice thing is both adapters are pretty compact, and not much larger in diameter than the camera lens itself. I got it for a song on EBay- maybe $15 shipped? (and it comes with a little case in addition to the VF!) Ironically I have a Petri rangefinder camera as well, but the adapters are for a different model with different filter thread. There are a couple of different sets available for different Petri cameras, all are apparently identical but with different filter thread size: Petri 1.9- 43mm filter thread (this is the one I have) Petri 2.8- 40.5mm filter thread Petri 7s- 52mm filter thread size So to use this you just need the appropriate inexpensive step down ring (~$2). If you don't have a filter thread adapter and just need one to fool around with this, there are ~$7 hood/adapter sets on EBay. Here are the samples. All shot at f/4 through my office window, AF was on the white truck (camera AF worked fine with both adapters): https://dl.dropbox.com/u/29935/Petri Tele Wide Adapter/normal.JPG https://dl.dropbox.com/u/29935/Petri Tele Wide Adapter/tele.JPG https://dl.dropbox.com/u/29935/Petri Tele Wide Adapter/wide.JPG Both adapters are sharp in the middle, but soft at sides and corners. A little vignetting, more so with the wide. The tele adapter should have some practical applications since you might not need edge sharpness (in fact the effect might even be desirable in certain situations.) If only it were 1.6-1.8x for a greater effect!! The wide adapter is probably impractical for real use, if it was wider then there might be a worthwhile tradeoff for certain shots. I don't have a step down ring but held the adapter in front of the camera lens. I think it worked fine since the centers are sharp. I could take more samples but I think these basically tell the story. Just search Ebay for 'Petri aux lens' and you will see some auctions, if you have patience you will never need to pay over $20-25 for the entire set including viewfinder if you want it. The viewfinder is nice and bright with 2 sets of frame lines for the wide and tele, though obviously not needed by x100 owners.