[Fully Serviced] [Yellowing Treated] [Clear] PENTAX SMC TAKUMAR 50mm f1.4 M42 The helicoid, aperture blades, and aperture ring function without any issues. Many of these lenses suffer from severe yellowing, but this one has undergone extended UV treatment to remove it. It appears completely clear to the naked eye. The price may seem higher compared to other yellowed lenses, but this lens is highly recommended for those seeking a clean and clear example. When using a mount adapter, please ensure it is for the M42 mount. This item is also listed on eBay, so please forgive us if it sells out. Size... Pentax M42 mount Focal Length... 50mm Maximum Aperture... 1.4