http://www.comingsoon.net/movies/news/629319-fantastic-beasts-and-where-to-find-them-photos-released#/slide/1
Boom Operators assist the Production Sound Mixer and operate the boom microphone. This is either hand-held on a long arm or dolly mounted (on a moving platform). If radio or clip microphones are required, Boom Operators position them correctly around the set or location, or on actors’ clothing.
Boom Operators are responsible for positioning microphones so that Sound Mixers can capture the best quality dialogue and sound effects. If this is done well, a great deal of money can be saved by not having to re-record (post-sync) the dialogue at a later stage.
Boom Operators are also responsible for all the sound equipment, ensuring that it is in good working order, and carrying out minor repairs where necessary.
Boom Operators begin work on the first day of principal photography. They have to read the script and familiarise themselves with the characters and their lines of dialogue. Members of the Sound Department arrive half-an-hour before call time, in order to unload and set up all the sound equipment.
Boom Operators are given “sides” (small booklets of pages from the script that are to be shot each day. They have to memorise all lines of dialogue and anticipate when to move the boom during filming. During rehearsals Boom Operators carefully note all planned camera movements and lighting requirements. They have to make sure that the microphone does not accidentally fall into shot or cast shadows.
Boom Operators are on set virtually all day. They work very closely with the Camera Crew. They are often asked to move slightly because of lights or camera angles and Boom Operators may also make similar requests. They finish work when the film wraps (is completed).
Most film sets are challenging environments for Mixers because there are often unwanted noises to deal with, or the required camera shots hamper the placing of microphones.
Approximately two weeks before the first day of principal photography, Production Sound Mixers meet with the Producer and Director. They discuss their creative intentions, (is the sound naturalistic or stylised, etc.), technical requirements and budgetary issues. They also meet with the Costume Department and Visual Effects Supervisors to discuss the placement of microphones on or around the actors, and visit all locations to check for potential sound problems.
When filming begins, Sound Crews arrive on set half-an-hour before call time to prepare their equipment. During rehearsals, the Production Sound Mixer and Boom Operator plan where they should place microphones to get the best possible sound quality. After each take, Production Sound Mixers (who are situated off set, but close by), check the quality of sound recording and, if necessary, ask for another take.
Production Sound Mixers work with the Boom Operator to select suitable types of microphone. They carefully reposition these microphones for each set-up, to ensure adequate sound coverage.
If music is required in a scene, Production Sound Mixers also set up playback equipment and speakers for the actors. At the end of each shooting day, Production Sound Mixers may send the day's sound recording files to post production. They also hand over originals to the Camera Assistant, who packages them up with the camera rushes. Production Sound Mixers finish work when the film wraps (is completed).
Production Sound Mixers work on a freelance basis on features and drama productions. The hours are long and the work often involves long periods working away from home.
http://creativeskillset.org/job_roles_and_stories/job_roles/3845_boom_operator_film
http://creativeskillset.org/job_roles_and_stories/job_roles/3836_production_sound_mixer