It has long been known in spectroscopy that light not passing through a sample, but reaching the detector (i.e., stray light), results in a distortion of the spectrum known as absorption flattening. In spectroscopy with crystals, one must either include such stray light or take steps to exclude it. In the former case, the derived spectra are not accurate. In the latter case, a significant amount ... [Show full abstract] of the crystal must be masked off and excluded. In this paper, we describe a method that allows use of the entire crystal by correcting the distorted spectrum.