Scope This procedure provides for two methods of data collection and calculation. In Method A@ the fiber deflection (tif)@ typically measured in pm@ is determined as one half the difference between the maximum and minimum fiber positions occurring as the fiber is rotated. In Method B@ the fiber position is measured at uniform rotational increments and the data fit to a sinusoidal function@ where the fiber deflection (6f) is calculated as one half the peak-to-peak amplitude of the best-fit sine wave.