Illustration of derivation process of the new PHOTOM. This example shows band 2C. The spectrum was normalised with respect to its maximum, and is unit-less. A spline is fitted through the chosen continuum points on the spectrum. This spline is then divided by the model spectrum to find the correction factors. The result from multiplying the uncalibrated spectrum by these factors (indicated by the arrow) is shown in orange, and matches the model.