||Optical methods or visualizations cannot be performed for granular flows because of the opacity of these materials. Hence, the efficient techniques developed for flow analysis cannot be adapted. This reduces possible methods to the use of expensive magnetic or radioactive tracking methods or X-rays visualizations. In this article, optical particle tracking velocimetry (PTV) is presented for a mixture of oil and glass beads by matching the index refraction of both materials.The mixture of glass and oil is nontoxic and is inexpensive enough to allow applications on large-scale devices. This article shows that Lagrangian observations of single-colored particles, as well as Eulerian statistical fluxes, are possible. Here the technique is described for a sedimentation flow of 3-mm beads in a squared-section vertical tunnel. It can also be applied, even more easily, for granular flows in liquid, because the bead agitation is generally less intense in this case.