These may be concentration differences due to evaporation of the liquid phase, or density differences, due to gas compression or expansion and turbulent mixing of gas flows. When illuminated, differences in the refractive index of the gas phase lead to an additional low angle light scattering signal. In the field of flow visualization, this effect is known as \"schlieren\" and is used for the investigation of shock waves and other flow phenomena in transparent media [11,12]. However,in laser diffraction measurements, this additional signal is interpreted as a droplet-caused scattering signal by the measurement system. As the low angle scattering signal mainly affects the measured light intensity on the inner detectors of the measurement device, the presence of large droplets is calculated by the mathematical inversion procedure [3; 4; 5]. The beam-steering effect must be considered, especially, when pneumatic atomizers are used. In pneumatic atomizers, the kinetic energy of compressed gas is used to deliver the necessary atomization energy. Expansion of the compressed atomization gas after leaving the nozzle leads to a significant decrease in density and therefore to a density gradient throughout the turbulently-mixed gas phase. In turn, this density gradient leads to a gradient in the refractive index of the gas phase. As gradients in density and therefore in refractive index increase with the pressure difference between compressed atomization gas and surrounding atmospheric gas, the beam-steering effect is especially observed at high input gas pressures [5]. When beam steering occurs, it is recommended both in the literature and by manufacturers of commercial measurement systems to deactivate the affected inner light detectors, correlated to the largest droplets [5; 13]. This detector deactivation leads to a reduction of the system's measurement range. By this procedure, apparent droplets, caused by beam steering, are no longer detected by the laser diffraction system and therefore do not affect the measurement result. However, this method of beam-steering correction is only applicable when real and apparent parts of the droplet size distribution are clearly separated from each other. But, when generated droplet sizes increase, the difference between the real and apparent part of the measured distribution gets smaller. From a certain point, both parts begin to overlap. In this case, it is no longer possible to find a measurement range that totally excludes the beam-steering effect from the measurement result, without excluding a part of the real droplet size distribution from the measurement result. As a consequence, in practical measurements, a wider measurement range has to be accepted, when real and apparent distribution parts are not completely separated and the method of detector deactivation is applied. Although, this distribution still includes parts of the apparent droplet size distribution. This leads to a systematic overestimation of large droplets in the calculated size distribution. Hence, the characteristic value x\({}_{90,3}\), correlated to the largest droplets of a distribution, is scarcely used in the literature in the description of atomization results of pneumatic atomizers. For this purpose, typically, the Sauter mean diameter (\(\overline{x}_{1,2}\)) is used, as subsequent process steps (e.g., heat and mass transport) are mostly considered to be surface controlled [1]. Additionally, this value is more robust than x\({}_{90,3}\) against the described misbalance in droplet size distribution, caused by the beam-steering effect. This means the value of \(\overline{x}_{1,2}\) varies little with changes in the largest droplet sizes, as the contribution of small droplets to the represented surface-to-volume ratio of a distribution is much higher.