Series Filters

Series filters
From the 1930s through to the late 1970s, filters were also made in a sizing system known as a series mount. The filters themselves were round pieces of glass (or occasionally other materials) with no threads or rings attached. Instead, the filter was placed between two rings; the mount ring either screwed into the lens threads or was slipped over the lens barrel and the retaining ring screws into the mounting ring to hold the filter in place. The series designations are generally written as Roman numerals, I to IX, though there are a few sizes not written that way, such as Series 4.5 and Series 5.5.


Series number filter size adapter ring
IV 20.6 mm 23.5 mm
4.5 25.5 mm  
V 30.2 mm 33.5 mm
5.5 35.9 mm  
VI 41.3 mm 44 mm
VII 50.8 mm 54.346 mm, 36 tpi thread pitch
7.5 57.0 mm  
VIII 63.5 mm 66.7 mm
8.5/5.5L 74.8 mm x 5.6 mm  
8.5/8mm 74.8 mm x 8 mm  
IX 82.6 mm 87.5 mm
93 93 mm  
103 103 mm  
107 107 mm  
119 119 mm  
125 125 mm  
138 138 mm  

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