If the measured optical density is to be expressed in relation to a culture parameter such as, for example, the cell number, it is necessary to calibrate the photometer. In order to determine the concentration of the cells, OD600 values are aligned with the number of cells of the cultured strain. Otherwise, there is a possibility that aberrant measurement values may lead to a false interpretation of the growth phase of the culture, and in the worst case, the subsequent experiment may not be successfully carried out.
 Janke SA, Fortnagel P, Bergmann R. Microbiological turbidimetry using standard photometers. BIOspektrum, 1999; Vol. 6: 501-502.
 Harnack K, Spolaczyk R, Janke SA. Turbidity measurements (OD600) with absorption spectrometers. BIOspektrum, 1999; Vol. 6: 503-504.