Blackmagic Design PL Mount Shim Kit

A set of spacer rings for the Blackmagic URSA camera bayonet mount. The rings are inserted between the bayonet mount and the camera body to adjust the back focal length so that the focus matches the scale on the lens.

Shims are inserted between the lens mount and the camera body. They adjust the distance from the sensor so that the distance to the subject corresponds to the focus marks on the lens. They are most commonly used with PL lenses—cinematographic lenses that are focused manually and have very precise scales on the barrel, so even a tenth of a millimeter is noticeable.

According to the manufacturer, Blackmagic URSA Mini cameras come with a 0.50 mm shim already installed. Shims are added or removed in 0.10 mm increments—for example, a 0.40 mm shim is installed instead of the 0.50 mm one—and after the camera is assembled, the result is tested with your own lenses to see if they hit their focus marks.

You’ll need an Allen wrench, a 2.0 mm screwdriver, and a torque wrench capable of precisely setting a maximum torque of 0.45 Nm. Throughout the entire process, the glass filter in front of the sensor remains exposed, so the camera is placed on a clean pad and no one touches the filter. During reassembly, the mount is tightened evenly and in the order specified by the manufacturer in the manual.