C-mount Lens Focus Gear Hack

Here’s a quick little show and tell/how-to for adding (semi)permanent lens gears to each of your c-mount lenses. For cheap.


I have a few of the Wide Open Camera zip gears and they are awesome. Albeit a bit pricey for some plastic and a couple of zip ties. They are a great option for some of my larger DSLR size lenses, but for for the 5 c-mount lenses I own, I found a better/more affordable option. Since most c-mount primes are fairly small and only take a minimum amount of force to turn the focus ring, using flexible gear ring belts works really well. But I don’t want to apply and remove these things all the time. So I tested cutting them to length and glueing them together around the barrel of my lenses. And because these are really inexpensive, I can have all of my c-mounts geared up and ready to go without any fiddling. And you don’t have to deal with the silly tightening knob banging into your follow focus or rails and generally getting in the way. Functional and aesthetically pleasing at the same time.

Flexible .8 gear ring belts can be found online between $5 and $7(and even less from China) and one belt, according to it’s length, can sometimes add gears to more than one c-mount lens due to their small diameter. So in many cases, thats $2.50 per lens. Not bad. Not bad at all.


Here’s what you’ll need:

• Super Glue – I like the Gorilla brand stuff

• X-acto knife

• Duck Tape

• Flexible gear belt

• c-mount lens

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Step 1: Chop off the tightening knob block. Use the x-acto carefully and make very firm, precise cuts to the gear belt between the gears(in the valley). A nice straight up and down cut is what you want.

Step 2: Wrap the gear belt around the focus ring of your lens. Allow the long end to overlap the nice clean cut you made in Step 1 and note where to cut it to length. Always cut a few extra valleys past where you think the proper length is. You can always cut a few more teeth off as you make it fit. These gear rings work well for this because there is a bit of stretch in them should you find that the length is slightly off. You may have to pull a bit tighter to get the ends to match up but this is a good thing and the glue dries really fast providing a nice hold.  They also have ridges on  the inside part of the belt which creates a nice grip on most focus rings without too much tension needed.

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Step 3: Apply a small amount of Super Glue to one end of the gear belt. Rub the two ends together, separate them, and then let the glue begin to tack up. About a minute or two. Because of the plastic compound used in these belts, the Super Glue really melts it’s way in there and creates a nice bond. Once the glue is becoming a bit stickier, I add just another little drop to one end to make sure there’s enough to cover the area when the ends are pressed together. A bit of overflow is not necessarily a bad thing here, but you don’t want so much that it spills out all over your lens barrel. Be conservative.

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Step 4: Because cutting the belt in the valleys allows for an almost perfect seam when the ends are glued together, you don’t have to worry too much about where the seam ends up around your focus ring. But, I took a close look at each of my lenses and where the follow focus gear would come in contact with the lens throughout it’s rotation. And, decided to place the seam on the “back side” of the lens where it wouldn’t have any contact at all. You’ll have a good hold that would probably stand up to the task, but why push your luck?

Step 5: Place the gear belt around the focus barrel of your lens and press the ends together nice and tight making sure everything lines up. If you allowed your glue to get nice and sticky, you shouldn’t have to hold the ends together very long before you have a nice bond forming. Once the ends appear that they want to stay together on their own, tightly wrap a piece of Duck Tape around the gear just to hold things together nicely. Walk away and don’t touch your lens for at least 30 minutes.

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Step 6: Carefully remove the Duck Tape and you should be ready to use your lens.

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What do you think?