Caveat: Detector transients are very often the limiting factor for the achieved accuracy. The PHT-P and PHT-C transient correction (Section 7.3.5) only works satisfactorily for measurements which are long compared to the detector transient time at a given illumination. Measurements flagged by the OLP software as `plateau data affected by residual drift' (Table13.3) can be unreliable due to a residual drift greater than 5%. Raster measurements with PHT-S generally suffer from transient effects, since a static spectral response function is applied.