mikhail_r

They are Goerz Dagor series III copies (except the Symmars are made of different focal length cells while the original Dagors were symmetrical). Any information you can find on Dagors is valid for the f/6.8 Symmars, too. For color imaging, the F/6.8 Symmars as well as the f/6.8 and f/7.7 Dagors and the series VII / VIIa Protars need a UV-blocking filter as all of them are very transparent in the UV - I mean a real filter like Wratten 2b, not a protector.