A process for producing an optical effect layer on a substrate comprising a photomask, said OEL comprising a motif made of at least two areas, preferably at least two adjacent areas, made of a single hardened layer, said process comprising the steps of: a) applying on the substrate comprising the photomask a radiation curable coating composition comprising one or more photoinitiators and a plurality of magnetic or magnetizable pigment particles so as to form a coating layer, said coating layer being in a first state and said coating layer at least partially facing the photomask; b) b1) hardening one or more first substrate areas carrying the coating layer through the substrate, said hardening being performed by irradiation with a UV-Vis irradiation source to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their positions and orientations; and c) c1) exposing at least one or more second substrate areas carrying the coating layer which are in a first state due to the presence of the photomask of the substrate to the magnetic field of a magnetic-field-generating device thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow any magnetic or magnetizable pigment particles orientation pattern except a random orientation; and c2) simultaneously, partially simultaneously or subsequently hardening by irradiation with a UV-Vis irradiation source at least the one or more second substrate areas carrying the coating layer to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their adopted positions and orientations, wherein the photomask has an optical density D M equal to or higher than 1.0, preferably equal to or higher than 1.1 and more preferable equal to or higher than 1.2. a) applying on the substrate comprising the photomask a radiation curable coating composition comprising one or more photoinitiators and a plurality of magnetic or magnetizable pigment particles so as to form a coating layer, said coating layer being in a first state and said coating layer at least partially facing the photomask; b) b1) hardening one or more first substrate areas carrying the coating layer through the substrate, said hardening being performed by irradiation with a UV-Vis irradiation source to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their positions and orientations; and b1) hardening one or more first substrate areas carrying the coating layer through the substrate, said hardening being performed by irradiation with a UV-Vis irradiation source to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their positions and orientations; and c) c1) exposing at least one or more second substrate areas carrying the coating layer which are in a first state due to the presence of the photomask of the substrate to the magnetic field of a magnetic-field-generating device thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow any magnetic or magnetizable pigment particles orientation pattern except a random orientation; and c2) simultaneously, partially simultaneously or subsequently hardening by irradiation with a UV-Vis irradiation source at least the one or more second substrate areas carrying the coating layer to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their adopted positions and orientations, c1) exposing at least one or more second substrate areas carrying the coating layer which are in a first state due to the presence of the photomask of the substrate to the magnetic field of a magnetic-field-generating device thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow any magnetic or magnetizable pigment particles orientation pattern except a random orientation; and c2) simultaneously, partially simultaneously or subsequently hardening by irradiation with a UV-Vis irradiation source at least the one or more second substrate areas carrying the coating layer to a second state so as to fix or freeze the magnetic or magnetizable pigment particles in their adopted positions and orientations,