i'm not sure about the fs100, but I know that for the af100 (and all m4/3 cameras), you can use the newer nikon g lenses if you bet a special adapter. It lets you stop down the lens, but you have no idea of knowing the number. Not ideal, but I know that some people use this technique when they want to use a newer lens for whatever reason. Also, I have heard great things about the 35mm f2 ais. ebay and keh are good places to buy, and it never hurts to wander around at garage sales and or craigslist when looking for older glass in general