Push On Filter Design

[BobUK]

Some of my vintage cameras have no filter thread on the lens, so push on filters have to be used.
Most of the filter mounts have a notch machined into the edge.


What is the purpose of the notch?

Thank you.

 

[koraks]

Maybe to accommodate any protrusion from the shutter or aperture system?

 

[JPD]

My Goerz Tenax needs it because the speed setting dial on the shutter is too close to the lens, and many front element focusing lenses have a peg that stops the focusing ring from going past infinity (and the closest focus).

 

[Ian Grant]

Some front cell focussing lenses have a protruding lug that stops focus at Infinity, and closest focussing, with a pin stop in the shutter.. So as JPD says

Ian