1. Method for the determination of a geometrical parameter for a mixture of fibres of different length and width, including, separating a quantity of fibres on a clearly defined surface of a substrate, producing an image of the separated fibres by means of a camera; and determining measured values, geometrical parameters of the fibres from the image, the improvement comprising: (a) producing two congruent images, (b) determining grid elements by means of a grid said grid elements are covered by the fibres, the grid having been chosen in such a way that one grid step is at the most as wide as the thinnest point of an individual fibre, (c) the images mutually displacing by one or more grid steps in one direction (x); (d) determining the number of grid elements with fibres of the two images which are mutually overlapping after the displacement, by means of a counter, (e) displacing the images from the starting position in a direction at right angles thereto (+x) and subsequently diagonally in the (x/.+-.y) direction by the same distance or distances; (f) determining subsequently the number of grid elements with fibres of the two images still overlapping after the displacements; and (g) adding the number of grid elements (surfaces) determined according to steps (b) through (f) and dividing the resulting sum by the number (F) of the grid elements determined according to step (b), so as to produce the desired parameter.