The Chinon Auto 55 mm f/1.7 is a vintage, standard PRIME lens for M42 screw-mount cameras, , it features a 6-element/5-group optical formula, ideal for low-light shooting and shallow depth-of-field. Its rendering is sharp at infinity from f/2.8 onward. The lens focuses down to 0.5 m, uses a 52 mm filter thread, and weighs approximately 210 g in a compact 61.5 x 41 mm all-metal barrel. Thanks to its M42 mount, the Chinon 55 mm f/1.7 adapts easily to modern Pentax DSLRs and mirrorless systems (Sony E, Canon RF, Fuji X, etc.) with a simple adapter-no electronics or modifications required. Focal length: 55mm Max length: 49mm + mount Max diameter: 61mm Weight: ~210g Aperture: f/1.7-f/16, 6 blades Min. focus distance: ~0.5m Filter diameter: 52mm All metal construction. M42