05 - Tips and Tricks for virtual camera calibration


During the virtual camera calibration inside Live FX, you might not always get expected results right away. There are a lot of variables at play, which often make it difficult to track down a specific issue. This article lists a few things to consider checking, when things are not optimal:

Lens Calibration

  • Double check the outcome by performing the calibration twice. The results should be close together.
  • Make sure the sensor data is entered correctly.
  • Make sure the sensor has the same aspect as the image. If the aspect is not the same it means that the image contains framing or is cropped and the calibration will not work.
  • Store the outcome in a Camera Profile, so you can easily re-use it later on.
  • Measure printed charuco and aruco markers accurately. The print program might have resized them when printing them and their dimensions might differ from the default in Live FX.
  • When on a large set, consider printing the markers in A3 size.
 Depending on the camera resolution and distance between camera and the marker, a bigger print might improve the detection.

Tracking Issues

  • Make sure the camera / live captures and the composition shot have the same framerate. Tracker data is tagged based on the timecode and different framerates might cause the tracker data to be associated with the wrong frames.
  • The tracker-vs-image delay might for some trackers vary a bit from one session to the next. Always do a quick test after the position calibration to ensure the entered delay value is still good.
  • When you still experience drifting after a calibration:
    • try manually adjusting the Focal Length. +/- 0.5 degree per try. Always followed by a "Set Position"on the origin Aruco marker. Then see if it improves or worsens the drifting.
    • try manually measuring and adjusting the tracker mount offsets. +/- 10mm per try on one axis, always followed by a "Set Position".
    • manually measure the mount (XYZ) offset from the Nodal calibration and possibly adjust it. Again followed by a "Set Position" and check if drift improved or worsened.
  • Do regular Set Position calibration. Some trackers have some drift on their own.
  • Some image based trackers have a hard time with a massive green-screen (without markers). Consider mounting the tracker at a different angle – e.g. pointing it at the ceiling. Make sure you (re)do a Nodal calibration to determine update the tracker mount offset.


Posted - Thursday, December 08, 2022 2:16:12 AM
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