The invention pertains to a apparatus for performing operations, in particular cutting, embossing, creasing, folding and/or sealing, on a moving web provided with a series of identical images, which apparatus comprises a sensor for at least partially detecting the images on the web, and a processing unit which, dependent on a comparison of the data obtained with the sensor and a reference, generates an output signal to be used for one or more of the said operations. The processing unit comprises a memory and is arranged to select at least part of the detected data, store the selected data in the memory, and utilize the selected data as the reference. The invention further pertains to module for performing operations on a moving web and method of generating an output signal.