3-D. The move from film to digital technology has greatly reduced the difficulty in use of these technologies with unpredictable behaviors, specifically via the use of continuous recording and post-triggering. With film high-speed cameras, an investigator must start the film then attempt to entice the animal to perform the behavior in the short time before the film runs out, resulting in many useless sequences where the animal behaves too late or not at all. In modern digital high-speed cameras, the camera can simply record continuously as the investigator attempts to elicit the behavior, following which a trigger button will stop the recording and allow the investigator to save a given time interval before and after the trigger (determined by frame rate, image size and memory capacity during continuous recording). Most software allows saving a subset of recorded frames, minimizing file size issues by eliminating useless frames before or after the sequence of interest. Such triggering can also be used to synchronize recording across multiple cameras. The explosion of alkali metals on contact with water has been studied using a high-speed camera. Frame-by-frame analysis of a sodium/potassium alloy exploding in water, combined with molecular dynamic simulations, suggested that the initial expansion may be the result of a Coulomb explosion and not combustion of hydrogen gas as previously thought. Digital high-speed camera footage has strongly contributed to the understanding of lightning when combined with electric field measuring instrumentation and sensors which can map the propagation of lightning leaders through the detection of radio waves generated by this process. Uses in industry When moving from reactive maintenance to predictive maintenance, it is crucial that breakdowns are really understood. One of the basic analysis techniques is to use high-speed cameras in order to characterize events which happen too fast to see, e.g. during production. Similar to use in science, with a pre- or post-triggering capability the camera can simply record continuously as the mechanic waits for the breakdown to happen, following which a trigger signal (internal or external) will stop the recording and allow the investigator to save a given time interval prior to the trigger (determined by frame rate, image size, and memory capacity during continuous recording). Some software allows viewing the issues in real time, by displaying only a subset of recorded frames, minimizing file size and watch time issues by eliminating useless frames before or after the sequence of interest. High-speed