A method for image acquisition of an object in transit on a movable supporting surface includes detecting a presence signal of the object in a preset position, and at least one dimension and/or position signals, the signals being generated by at least one sensor arranged upstream of a linear camera; detecting a “trigger event” signal, generated on the basis of the presence signal, the linear camera starting to acquire an image on the basis of the “trigger event” signal; starting to acquire an image of the object, when the object has travelled a preset distance from the preset position, the distance being calculated by an advance sensor suitable for generating a signal comprising an electric pulse at each preset movement of the movable supporting surface; and setting a mode for image acquisition of the linear camera on the basis of a resolution of the advance sensor.