thumb|right|Rubinar 1:5.6 500 mm Rubinar () is a Soviet lens design series developed and produced by JSC Lytkarino Plant of Optical Glass (LZOS). It is compact despite its long focal lengths.
thumb|right|Rubinar 1:5.6 500 mm Rubinar () is a Soviet lens design series developed and produced by JSC Lytkarino Plant of Optical Glass (LZOS). It is compact despite its long focal lengths.
Rubinars can be used with proprietary mount cameras by using M42 adaptors. Focusing motors are absent though (manual only), and so are the variable apertures.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).