Karl Norris pioneered the field of near-infrared spectroscopy.  He began by using log(1/R) as a metric of absorption. While often the samples examined were “infinitely thick”, partially transparent samples were analyzed (especially later) in cells that had a rear reflecting surface (reflector) in a mode called "transflectance". Therefore, the remission from the sample contained light that was back-scattered from the sample, as well as light that was transmitted through the sample, then reflected back to be transmitted through the sample again, thereby doubling the path length.  Having no sound theoretical basis for data treatment, Norris used the same electronic processing that was used for absorption data collected in transmission.  He pioneered the use of multiple linear regression for analysis of data.
Gerry Birth was the founder of the International Diffuse Reflectance Conference (IDRC).  He also worked at the USDA.  He was known to have a deep desire to have a better understanding of the process of light scattering.  He teamed up with Harry Hecht (who was active in the early meetings of IDRC) to write the Physics theory chapter, with many photographic illustrations, in an influential Handbook edited by Phil Williams and Karl Norris:  Nearinfrared Technology in the Agriculture and Food Industries.