In this study we introduce the time-shift technique, also known as the pulsed-displacement technique, as a means of measuring size and velocity of spherical particles. The measurement technique is not new, it has been introduced by Semidetnov<sup></sup> in 1985 and more generally discussed by Hess and Wood<sup></sup>, Lin et al<sup></sup>, Damaschke et al.<sup></sup> and Albrecht et al<sup></sup>. The novelty introduced in this study is the application of the technique to measure non-transparent particles, which are quite common for example in spray drying processes or in paint sprays. In this contribution the basic working principle of the time-shift technique will be reviewed and an optical configuration suitable for the measurement of non-transparent droplets will be presented. The signal generation and processing will be discussed. Example measurements in a milk spray are presented.