Shimming The Pl Mount - Blackmagicdesign Blackmagic URSA Installation And Operation Manual

Shimming the PL Mount

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Removing and replacing the PL Mount
Step 1.
Place Blackmagic URSA or URSA Mini on a solid,
clean bench top and remove your lens or dust cap.
The glass filter covering the sensor will be exposed
for the duration of the shimming process, so it's
important to keep the filter as clean as possible.
Be careful not to touch the filter while shimming
the PL mount.
Shimming the PL Mount
What is a Shim?
Blackmagic Shims are thin disks of varying thickness that let you make fine adjustments to the distance
between your PL lens and Blackmagic URSA or URSA Mini's sensor. This distance is commonly known
as the flange focal distance, or back focus, and can change slightly due to variables such as lens age
and the environmental conditions of your shoot. The PL mount is designed so you can easily adjust the
back focus using shims.
Shims are placed between the PL mount and the camera body so the distance from your subject to the
sensor matches the focus marks on your lens. Your Blackmagic URSA or URSA Mini is supplied with a
0.50mm shim already installed. You can purchase shim sets of varying thickness from your local Blackmagic
Design reseller. Use shim thicknesses depending on your back focus requirements.
To shim your camera's PL mount you'll need a torque wrench able to accurately set a maximum torque
of 0.45Nm, with 2.0mm and 2.5mm hex key drivers.
Step 2.
Remove the six PL mount screws using the 2.5mm
hex key. You may need to occasionally rotate the
PL locking ring clockwise or counterclockwise to
access the screws.
Step 3.
Carefully lift the lens mount away from the camera
body. Keep the screws safely located close to the
lens mount.