Small, fast, and inexpensive in-line spectrophotometers can produce
in-line spectrums of a substrate before or after printing on the
substrate. In-line spectrums are generally far less complete than a
reference spectrum produced with a large, slow, and expensive reference
spectrophotometer. An in-line spectrum can be mapped to a reference
spectrum using a variety of known algorithms. However, the mapping is
erroneous when the media substrate type changes. Reference transform
matrices and in-line transform matrices can correct the erroneous
mapping.