The "A" series of Pentax lenses introduced electrical contacts to the K-mount, allowing for the "Auto" (A) position on the aperture ring. When set to this position, compatible cameras like the ME Super (in Program mode) or Super Program can control the aperture electronically. This lens features the Super Multi-Coating (SMC) that Pentax is famous for, which significantly reduces flare and ghosting. The 50mm f/2 was often the standard companion for the Super Program and Program Plus bodies. It is widely respected for being incredibly sharp and compact, often outperforming much more expensive glass when stopped down.