editor is the artist
on the creative team who is tasked with molding all the production elements (raw footage
and sound, specifically) into something coherent
and hopefully entertaining.
Editing is the essence of cinema. It is what sets filmmaking apart from all other visual arts. Without editing, the content of all films would be limited to what can be done in a single take before the film magazine runs out. Editing allows the story of an entire lifetime or the events of a single second to be played out in two hours. Editing will fool you, the viewer, into believing that two people are in the same room at the same time talking to each other when, in reality, the Leading Man is on a soundstage in Hollywood and his Love Interest was shot on location in Prague six weeks earlier.
On an ideal job the editor is hired during pre-production. This is somewhat common in the world of feature film production, but exceedingly rare for anything related to television such as commercials or music videos. The earlier in the process the editor is brought on, the more opportunities he or she has to provide creative input about what can be done during production to help achieve the director's vision during post-production.
The editor is given the dailies (the footage as shot) and the production sound (sound recorded at the shoot). He or she must sift through all the takes of all the angles of all the cameras used and find the gold; the best moments judged by many criteria. Is the acting here great or crap? Can we use this reaction shot against that other line? Do the eyelines match? Nuances and subtleties are just as important as the big stuff: what's the coolest angle on that explosion?
The process of editing is making choices. When do you cut to a different shot, what shot do you cut to and why? How long should we see this close up? How long should that dissolve be, or should we do a wipe instead?
The editor and the director work together to mold the best film possible out of the available material. Once you're in the editing room, what you wanted to shoot is irrelevant. What's important is what you actually have. On some features the editor has the luxury of ordering (requesting) reshoots, or that another angle be covered, or that a cutaway be shot. This happens very rarely on smaller-budgeted projects. As such, seeing the possibilities is one of an editor's greatest skills.
It is the editor's job to create and maintain an entertaining pace for the overall film. A film should ebb and flow, pull the viewer along for a while and let them breathe at other times. The climax should feel, to the viewer, as if it has arrived at exactly the right moment. It is in the pacing of a film that entire scenes may often be removed, added, or significantly altered. The primary reason all those deleted scenes exist to be packaged on DVDs is that they knocked the film off pace when included originally.
The editor is a huge part of making all the decisions which finish a film, from the tiniest details (this shot is two frames too short) to the largest problems (our film is half an hour too long). A movie, or television show, or commerical, or music video comes togther underneath the editor's fingers. It's creation magic, and that's why I love being an editor.