Disclosure relates to a method and a device for determining the distribution and orientation of platelet-shaped pigment particles over an extended region of an optical effect layer (OEL). The method includes a) taking at least one image, under illumination of said extended region of the optical effect layer with collimated light incident from at least one first direction, of reflected light of said extended region of the optical effect layer from at least one second direction, using a telecentric lens-and-camera assembly having the optical axis of the telecentric lens oriented along said second direction, and b) processing the at least one image of said extended region to extract quantitative particle distribution and orientation information. The device includes a) a collimated light source for illuminating an extended region of the optical effect layer with collimated light from at least one first direction, and b) a telecentric lens-and-camera assembly for collecting the light reflected from said extended region of the optical effect layer into at least one second direction.