In 2008, Sequoia Scientific’s Dr. Ole Mikkelsen co-authored and published a paper; The Influence of Schlieren on In-situ Optical Measurements Used for Particle Characterization. This paper was based on data collected during his postdoctoral work in Canada and the UK between 2002 and 2007. It was published in Limnology & Oceanography: Methods in 2008. This lecture presents the results of that paper.