27 Dec 2018

Sigma 8-16 EF to PL and gear manual Conversion

This is the initial prototyping of a Sigma 8-16 EF lens into a geared manual PL mounted lens. The pl mount itself is milled from aluminum 6061 and the foundation model was something I drew up a while back and available on GrabCAD ( The rest is 2D printed with ABS plastic for the time being, it fits but rotation is tight and very rough. This isn't a complete rehousing like other cinema lens conversions would do, I still utilize the original internal mechanics and primary housing of the lens with all the electronics ripped out. Designing a geared focus and zoom rings was fairly simple to do that utilizes the original mechanics minus the infinite spin. The difficult part is the desiging the apreture ring and I'm guessing the reason not many of these type of lenses get converted without a full rehousing. Since pretty much all of these electronic lenses uses a miniature motor to control the aperture blades, so they are able to bury the actuator for the blades deep inside the lens housing. Luckily, in this lens there is just barely enough room to run a "slider" of sort up from the blades to where the apreture ring right next to the pl mount. At least it should work theoretically, the 3D printed plastic version is too soft for it to work effectively. Next step is to figure out how to machine these geared rings without a 4-Axis CNC mill.

The flange focal distance can be easily adjusted by placing shims in between the PL mount itself and a internal collar that attaches it to the lens main housing. I don't have my Red camera on had at the moment to show photos through this lens, so the photos of it mounted on my 3D printed directors viewfinder will have to do for now hehe. I'm also currently working on a way to machine new DVFs out of aluminum instead of these 3D printed ones with a slightly different design and improved optical layout. 

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Last modified on Wednesday, 02 October 2019 04:05

A little about me

profile.largeGeorge Tsai attended California State University, Long Beach and graduated in 2010 with BS in Electrical Engineering, Audio Engineering, and an Entrepreneurship Minor. He is also a United States Marine with combat deployments to both Iraq and Afghanistan. He concluded his service with an honorable discharge as a Sergeant. Today, he freelances in the film industry with his Red Epic-X camera package and production audio equipment. He is also the founder of FUZE Ti.  Read more...

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