Anamorphic Day-to-Day

Chop Shop – 3D Printing Focus Gears

August 21, 2016

First video that isn’t directly anamorphic, but still geared (pun intended) to save you some money and empower you to make your own seamless focus gears!


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Tito Ferradans here for the first non-anamorphic tutorial. Some of you might’ve read me saying that – for The New Romantics pilot episode – I tweaked up my Contax Zeiss lens set. I added Leitax mounts to all of them, getting rid of adapters’ wiggliness and, most relevantly than this, I added focus gears to all five lenses (28, 35, 50, 85 and 135mm). Instead of buying focus gears and switch them from lens to lens – which would’ve taken too much time on set – or buying a ton of those straps of gears and then fitting them to every lens, I took the most direct route and 3d printed them. As 3D printers become more and more popular, I thought it would be a useful tutorial.

I (not so) recently got a Micro 3D Printer, which is tiny but big enough to print focus gears for most lenses, with a print area of about 10x10x10cm. The next step was going to Thingiverse and downloading a free project for seamless gears – the original maker recommends ABS plastic, but I only had PLA, so I’m here to assure you both materials work just fine. To fully enjoy the beauty of this file, I recommend downloading OpenSCAD and playing with the customizable file. Now that the software was kind of ready, I went back to the lenses. Doing the first one is the hardest part – especially for me, that had never 3D printed in my life – and it took me FIVE days. After that, I was getting two done per day.

I’m going off the subject. Back to the lenses, using a caliper, measure the diameter of the focus ring – in millimeters. BE. VERY. PRECISE. For this Tokina 28-70mm, I measured 80.45 mm so I’ll add 0.15mm to that number and input this information into OpenSCAD.

The file you got from Thingiverse has three customizable parameters. The first parameter is the number of teeth. It affects how wide the gear is going to be. For a set of lenses, I like to keep the number of teeth constant so I don’t have to even adjust the follow focus after switching lenses. A thicker gear is also much more resistant than a thin one. The second of of them is the diameter of the hole where the lens should pass. I prefer to make this a tight fit so I can sand it down if it’s too tight. If it’s too lose, you gotta print another one. The third parameter is the height of the gear. Some lenses have a lot of travel when focusing – like the Iscoramas, Rectilux or Focus Module for example – so having a regular, 10mm gear, isn’t enough as it will travel off the follow focus’ reach. Make it thicker to ensure your follow focus won’t slip off during operation. You can also get this measurement with a caliper.

Now that all the numbers are in, run the script (F5), create the model (F6) and export the STL for print. Every 3D printer’s got their own software, so just load up the model and the important part is to set the right resolution. As this is a precision part, I had good results with 150 micrometers and filling it so the space inside the gear is solid instead of hollow. Did I mention 3D printing takes forever? A focus gear takes an average of six hours to print, so be patient.

*elevator music*

After it’s done, get rid of any imperfections by sanding them away. I always used a coarse – 80 grit – sandpaper, but you can use a thin one for a finer feel. Usually the gear doesn’t fit the lens right off the bat – which is good because it has to be tight – so the process is to do a bit of sanding, then test it out. More sanding, more testing. Getting it in is also another interesting step, as you don’t want it to simply slide in – that would be too lose. Fitting it is a constant challenge of leveling down the gear on the lens’ body a few millimeters at a time. Wiggling and patience are your best tools. You WILL have sore hands after doing this for a while. Also, lenses that have a rubber ring are better fits than the ones that are plain metal, since the rubber helps a lot with grip.

After this, you’re pretty much done. Just put the lens on the camera and get your follow focus running! I hope you found this tutorial useful and I’d be more than glad to see the results you get from it! Be patient all throughout. It’s a slow process, but comparing the costs to the results, it’s definitely worth your while. This is a different tutorial than usual, since it’s not DIRECTLY related to anamorphic – even though you CAN (and should) make focus gears for your scopes – so subscribe and be sure to check the archives to get addicted to anamorphic shooting. See you soon, Tito Ferradans out.

A photo posted by Tito Ferradans (@tferradans) on