This Canon 50mm F1.4 Fl mount lens started out life on a Canon Pellix. I put a 58/1.2 on the Pellix, sold the camera years ago. Remember when F1.2 Manual Focus lenses were $50 at camera shows? Before u43 cameras came out they were! Kept the 50/1.4 lens. FL mount lens are very well made, smooth operation, great optics. Stop-Down metering was their Achilles heel, which the FD mount corrected. I have the 50/1.4 SC on a Canon EF and the SSC on an F1. Canon Camera Museum | Camera Hall - Lenses (FL Mount) This one is now in Leica M-Mount, RF coupled. Stop-down metering is not an issue on an RF camera. "Ingredients", 1 Canon 50/1.4 FL mount lens, 1 old leg from a broken tripod, 1 retaining ring from a parts Jupiter-3, a $40 FotoDiox Canon FD to Leica M-Mount adapter, and some tape. Used a pipe-cutter to get the small extension tube, filed and sanded until it was ~14.75mm. Retaining ring fit onto the end of the tube, just the right diameter for an RF cam. This is the "Fit and Finish" part of the job. Required two iterations to get the thickness correct. final "Shim" for focus to agree with the camera, two layers of industrial strength plastic tape (~0.08mm) between the tube and the cam. Sharpie pen used to blacken the tape.