Easy-to-handle, environmentally-resistant digital stroboscopes dedicated for printing machines. Equipped with a rubber guard at the front to protect the stroboscope against shocks. The totally-enclosed drip-proof structure prevents water and dust from entering inside. It is possible to move a stop-motion image forward or backward while maintaining synchronization, in order to move the register mark or a picture to an easily visible location. A detachable connector cable is used for the power supply, which allows it to be easily repaired in the event of disconnection.