Abstract: This invention relates to a method and apparatus for dynamically measuring relative amounts of particles having differing optical properties and/or shapes in a mixture, comprising an inclined path down which the particles travel, a feeder to present particles to the inclined path, a source of illumination to illuminate the particles on the inclined path, an image receiver to record reflective-light images of the particles and a composition calculator to determine the relative amounts of the particles based on the reflective-light images.