Figure 9. Deviation of traction magnitude (DTM), and signal to noise ratio (SNR) for different traction magnitudes, expressed as a percentage of Young’s modulus of the substrate.

Up to a certain magnitude, the influence on the result remains small. However, for large traction and large adhesions, displacements are too big and the tracker fails to correctly match the bead displacements. If these are too small, the signal is of the same magnitude as the background noise, therefore resulting in lower SNR values.