RING-FOCUS BELT CANON 70-200mm f/4

Ring to focus a Canon 70-200mm f/4 lens using an electronic focuser (e.g. ZWO EAF) and a 3D printer belt. Requires a 10mm or longer M2 screw and hex nut.

The ring does not have teeth but instead uses screws or pins to hold the ends of the printer belt. This reduces backlash and allows the use of an open belt cut to the required length (about 33 cm / 13 in belt length is required).

The ring is designed for the Canon 70-200mm f/4 lens but may be used with other lenses having an outer diameter of 74mm.

Optional ZWO EAF bracket: https://www.printables.com/model/436289-bracket-eaf-zwo

Other sizes:

I had multiple requests to create similar rings of different sizes. Instead of answering each request individually, I am providing a link to the parametrized CAD model in Onshape (free for hobbyists): https://cad.onshape.com/documents/03b9604966ae1a3fc3f6e761/w/7eddff608c1112e3b9a089d6/e/961e1eb8b59661400f4910d2 Different sizes can be generated by changing the value of the InnerDiameter variable. If you publish a ring of a different size for another lens, please ensure to mark it as a remix of this one.