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I have a Bolex lens (filter) question for you Bolex experts:

On many of the Kern D-mount lenses (for the 8mm cameras) the thread size is 21mm . This takes a retaining ring and lens hood (Bolex catalog code: “ADUNI” ) . You screw in the retaining ring, then drop in a Series 4.5 filter , then screw on the lens hood to hold the filter in place.

 

I have found the selection of Series 4.5 filters to be limited and hard to come by. I want to attach a step-up ring to be able to use more commonly found 37mm or 43mm filters. I have found a 21mm to 37mm step-up ring on eBay which I hope will fit the thread pitch on the Kern lenses … OR my other thought was whether it would be better to leave the Bolex retaining ring on the lens and attach the step-up ring to the retaining ring ?

However, I don’t know exactly what the thread size is on the upper part of the retaining ring … it’s slightly wider than a Series 4.5 filter (25.4mm) … according to this website: https://www.apotelyt.com/photo-accessory/series-filters Series 4.5 filter retaining ring size is 28.6mm … I have seen Step-Up rings listed for 28mm to 37mm or 28mm to 43mm . Would a 28mm step-up ring work or do I need a 29mm step-up ring ? (I’m not seeing such a thing as a 29mm step-up ring available , so I’m hoping 28mm will work ) . See the photos.

 

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53657180_10215174149321985_7355609996706

53093800_10215174148961976_5317264946621

 

53185804_10215174149201982_7928036224235

 

53317844_10215174148801972_6717028138808

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A lot of the small series adapters snap on to the outer diameter of the filter ring and don't use the lens filter threads at all.

The part that grabs onto the lens is segmented and has a certain amount of elasticity to attach securely.

Maybe that's what you should be looking for instead. Measure the outside diameter of your 5.5mm lens to start.

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A lot of the small series adapters snap on to the outer diameter of the filter ring and don't use the lens filter threads at all.

The part that grabs onto the lens is segmented and has a certain amount of elasticity to attach securely.

Maybe that's what you should be looking for instead. Measure the outside diameter of your 5.5mm lens to start.

 

Yes, I have some of the slip-on series filter adapter rings that work. (although that still means I have to find old Series V or Series VI drop in filters , not the modern screw-on filters) .

 

The 24mm adapter fits on some of the Kern lenses (but not the Kern Switar 5.5mm f/1.8, which has a wider rim ... I think I need to find one that is 25mm or 26mm to fit the Switar 5.5mm f/1.8 ).

 

But I was just curious about whether anyone knows the exact thread size of the Bolex retainer ring shown in the set of photos above , to see if I can use a threaded step up ring that is 28mm (?) to 37mm . However, I suppose I just need to buy the 28mm to 37mm step up ring to try it.

 

[this shows a Kodak Series V adapter 24mm , which will fit around the rim of this Kern Switar 12.5mm f/1.5 lens]

53371906_10215179366092401_1959634087849

 

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