Setting Camera Offset

The coordinate origin of the Intersense is the center of the back of the camera. To set the virtual imaging plane to match that of the physical film or video camera, an offset needs to be added.

The Tracker to Camera Offset tab provides this adjustment. The offsets are measured from the tracker (in this case the Intersense) origin to the center of the camera’s imaging plane. Most cinema type cameras will have a mark on the camera body to show where this is.

The axis sign orientation is:

  • Axial: + goes towards the front of the camera
  • Vertical: + moves upward
  • Laterial: + goes toward the right of the camera, facing the same direction as the camera lens

Verify in Observer View

Use Observer View to verify that the offsets are going the correct direction.

In most camera mounting cases, the Intersense and Airtrack will be over the zoom lens barrel, which will result in negative values for the axial and vertical offsets, as shown above.

Measuring Positional Offsets

The best tool for this is a very large caliper (50cm).

McMaster-Carr part number: 19185A41.

Verifying Positional Offsets

Verify that the offsets are correct by setting the camera level, and measuring from the center of the camera lens barrel to the floor. The distance should be within a cm or 2 of the Y position shown in the Previzion user interface. If it is off by a long range, there may be a mistake in the axis sign in the Tracker to Camera Offset tab.

Last Modified: July 22, 2011