Extended Reel is a Gene Tonic in BioShock 2 that increases the time the camera records when researching. If the target is killed before filming stops, the player earns a higher score, and Extended Reel gives the player more time to make the kill.
Extended Reel can also work against the player if filming of a common target has started and a less common target such as a Brute Splicer or Alpha Series comes along, since filming cannot be stopped and restarted manually. Or you can start filming the new target, ending the previous recording of the other target.