Last year I aquired a 720nm Infrared Converted Fuji X-E1 and I performed a test with my then current lineup of Fujinon lenses to see which could be used for Infrared photography, and which couldn’t due to the phenomenon known as hot spotting. These hotspots usually manifest themselves as bright circle in the middles of the image, somewhat like a really bad lens flare. The reasons behind the hotspots can be attributed to the way Infrared light reacts with the coatings inside the lens barrel, or the coatings on the individual lenses themselves within the lens barrel. Part 1 of the test can be seen here.
Fuji Lens Testing For Infrared Hotspots Part 2