In the case of a method for sensing a marking (2) of a running web of material (3), the web of material is optically scanned by an image recording device (6). This generates in successive measuring cycles image signals which are fed to an image processing device (7). This image processing device (7) determines the positional values of the marking (2) of the web of material (3). A validity signal is generated from these positional values by applying a position-dependent weighting function and is output. This validity signal indicates whether the currently determined positional value is valid.