Make a photo lens work like a cine lens

1. A focus gear that fits

Cine lenses have gear teeth built into the focus ring. Photo lenses have a rubber grip. A follow focus or motor needs teeth, so the first step is a gear ring.

Rubber strap gears exist and they work in a pinch. A ring made for your diameter sits evenly on the grip and does not leave a strap end sticking out. It also lets you choose the width, so it does not cover the aperture ring.

• Measure the band where the gear will sit (here is how).
• Print a free slip-on ring to test the fit.
• If the ring needs to hold harder, use a clamp ring with three set screws.

2. The same gear position on every lens

When every lens gets a gear with the same outside diameter, the motor or follow focus stays in place when you swap lenses. Choose Outside Ø in the generator and use one number across the set.

3. Ends the motor can find

Wireless focus motors calibrate by turning the lens to both ends of its focus travel. Many photo lenses do not have a hard mechanical end: the focus ring keeps turning, or it slips past the end. The motor then calibrates on the wrong range.

Printed hard stops add two physical ends exactly where your focus travel starts and stops. They are calculated for your lens and for your motor's gear, so they need two measurements: the focus travel with tape, and your motor model or tooth count. The hard-stop generator walks you through both.

A note for focus-by-wire lenses: if the same ring movement does not always give the same focus change, physical stops alone will not make it repeatable.

4. Caps that fit and get noticed

Photo lens caps are made for camera bags, not sets. They are small, black and easy to lose in grass. A slip-on lens cap sized to the front of your lens is a free download; with your lens name and focal length on it, you find the right lens in the case without opening every cap.

Print a test ring first: the cap's fit depends on your material and printer as much as on the numbers.

5. Write the numbers down

Every ring from the generator has its dimensions engraved inside. Keep a note of the diameter, width and motor for each lens anyway. When a gear breaks on day three of a shoot, you will want to print a new one without measuring again.

Start with your lens in the lens library, or measure it yourself.