Archive: https://archive.today/nqjod From the post: >>When you watch a movie and see those perfect focus switches or zooms, the chances are you’re not seeing the result of the cameraman or focus operator manually moving the lens controls. Instead, they will have been planned and programmed in advance and executed by a motor. If you take a close look at many lenses you’ll see a ring that’s more than just extra knurling, it’s a gear wheel for this purpose. Want to experiment with this technique without buying professional grade accessories? [l0u0k0e] has you covered with a 3D printable focus zoom motor accessory.