Particles are suspended homogeneously in a carrier liquid. They pass through a thin flow cell in the optical path. Light is transmitted through the flow cell, thus projecting silhouettes of the particles onto a high-resolution camera sensor. The high frame rate and high resolution of the camera combined with a high-speed host computer enables the characterization of thousands of particles per second in real-time. This technique is ideal for applications where shape, not just diameter, is critical information for predicting raw material performance.