Hello I have these three yellow LZOS filters. I numbered them 1, 2 and 3 (in Red). Based on the inscriptions shown is it possible to establish an equivalence to standard Western filters classification ?? If yes, please let me know. Thank you in advance. Joao
you can find the information on https://www.zenitcamera.com/qa/qa-filters.html (in russian :) ) There is a table on that page, the 1st column is the russian filter type, the 2nd is the international filter type and the 5th is the glass type. The older russian filters till 1974 were marked with the glass type and the newer ones with the filter type. So on your photo number 1 is Y2x produced after 1974, number 3 is the same Y2x produced before 1974 and number 2 is Y1.4x