Kalimar was a distributor for re-branded cameras, lenses, etc. Their products were made by Cosina, Seagull, Zenit and a few others. Their products varied in quality. This lens was probably made by Cosina for Kalimar and paired with their re-branded version of the Minolta X300s. Most 50mm lenses are designed like the Contax Planar. It is a standard design. Because of this most 50mm lenses are excellent, including those made by third party manufacturers. Only a few stand out as being 'bad'. Yungnuo has managed to make a bad 50mm. Optically it is soft at f1.7. No surprises there. It sharpens up nicely by f4.