The invention relates to a method, the method comprises exposing an image frame of an object to be monitored by an area image sensor, transmitting a part of the exposed image frame to an image data processing device, analyzing the part and if the part is detected to comprise a predefined event, said image data processing device is arranged to transmit a trigger signal for triggering said area image sensor so that said area image sensor transmits a bigger part of at least one further image frame to said image data processing device for further analysis, and if not the area image sensor continues to expose at least one further image frame and to transmit a part of said at least one exposed further image frame. The invention further relates to a machine vision system for performing the method and a computer program product comprising instructions to perform the method.