Step 4 – Camera Calibration

Click on the New Page icon .
Enter 2D view and first physically remove all reflective objects, such as the calibration kit or similar reflective equipment, from the measurement volume.
- Go to the Camera settings sidebar on the right side of the 2D view. Click on Enable for Marker masks.
- Click on “Auto-create” and start. QTM will mask all unwanted reflections. For manual masking options and advanced handling of camera settings and marker masks, please refer to the QTM Manual.

Place the L-shaped calibration reference on the floor.

Precise alignment is critical for the calculation of the joint moments/power.

The correct placement depends on the convention that was used when setting up the force plates in QTM. Either the X- or Y-axis must be parallel to the intended walking direction but it does not matter whether the subject walks in positive or negative X/Y-direction.

The L-frame must be always placed on the same force plate, and in the same corner. We recommend that you take a picture of the default placement of the L-frame and put that picture in your lab.
The corner of the L-frame must be placed exactly on the corner of the force plate.
The long axis of the L-frame must be aligned exactly with the edge of the forceplate. If your L-frame has force plate alignment aids, use them for better alignment. The alignment of the short axis is not critical.
Always use height adjustment screws so that both axes are horizontal (use the spirit level gages for guidance). Avoid changing the setting of the screws between calibrations.

To calibrate, click on the calibration tool on the top menu bar.
A window will open that will ask how long you would like to capture. 20-30 seconds is a sufficient amount of time for a standard full body volume. For large volumes, increase the time so that you have enough time to cover the complete volume that will be used.
Click start and you will hear a bell. Using your calibration wand walk around the capture area and wave the wand in the area that the subject will be moving in. Note: for guidance how to move wand in the volume refer to QTM user manual in the section Making a measurement > Calibration of the camera system > Wand calibration method.
Stop when you hear another bell.
Confirm that the average camera residual is approximately 1-2 mm or under. Each camera should have collected at least 300 points. The standard deviation of the wand length should be 1-2 mm or better for a full body volume.
If you use the C-Motion Caltester, now you can perform a test to ensure the L-frame was aligned correctly and the force platform settings are correct.