- Shoot a step wedge or known thicknesses in the same exposure.
- Open the Measure panel (ruler icon) and the Thickness tab.
- Choose + Calibration box, draw a box on one step and enter its thickness in mm. Repeat for each step: at least 2, and 3 or more adds a beam-hardening correction.
- Optionally enter the Detector offset (dark level).
- Check Fit R². If the panel warns the curve is not monotonic, check the boxes.
Use the calibration
- Hover anywhere to read the thickness at the cursor.
- Draw a Thickness ROI to get its minimum.
- Tick Show thickness map to colour the image: thin areas are red, and faint colour means outside the calibrated range. Set the range with Map from / to (mm) and the Opacity.
- The line profile can plot thickness in mm.
- Tick Use this calibration for the other images in this session to carry it to the next images.
Readings outside the calibrated thicknesses are extrapolated and marked as such. Calibrate across the range you need.