First of all, what is it?
For a comprehensive definition and history, here’s the Wiki.
In short, in the early days of linear film editing (and tape editing) of documentaries, interviews or dramatic films, the main scene, master scene or main interview was strung together on one roll of film or tape called the A roll. Wherever that scene was to cut to another shot (a cut away, an insert or simply another scene not from the main scene) the A roll would get a piece of opaque leader and in the corresponding blank spot, the appropriate shot would be synced up on the ‘B roll’, itself separated by opaque leader which corresponded to those parts of the ‘A roll’ that were meant to be seen.
Later it would all be married up. This procedure is what made editing ‘seamless’ (otherwise you’d see constant flashes every time two pieces of film were joined together with editing tape). It also allowed for seamless transitional treatments (such as dissolves, fade to black, etc.)
These days it’s all done on computer—even features shot on film. The film is transferred to video where it is edited and then output back to film. Computer editing programs, of course, are called non-liner editing systems where you can simply drag and drop shots, transitions, effects, etc. with impunity. It’s intrinsically seamless.
Anyway, while B roll retains its original meaning, it has also modernized itself through the magic of Time and Slang.
Today in corporate video work, wedding videos, events we generally mean B roll to be any shot that’s not part of the narrative (such as an interview) or story, such as a scripted film. In film they generally call this ‘coverage’, which means you shoot a bunch of detail shots (the clock on the wall, the leaves blowing on the trees, birds in flight, people walking down the street, etc, ad infinitum) that might come in handy for the editor if he’s in a tight spot. Great film makers with large crews usually plan their films to the nth degree and specify all these things. Even then, smart cameramen shoot more than was asked for even by a detailed script.
In the run and gun category, when you don’t have crew support (assistant directors, script supervisors, etc.) B roll is essential. It will be, in fact, the main pictorial content of your video.
Let’s say you have a 15 minute interview. Or even a 3 minute one (in final edited form).
Who wants to see a talking head for 3 minutes or 15 minutes straight?
More to the point, most interviews of any length have to be edited. How do you cover up the cuts?
But the purpose of B roll isn’t just to cover up cuts. Yes, that’s where it can save your bacon when you found yourself forced to do an edit and have absolutely nothing relevant to cover it with. More importantly, B roll should help forward the story of the narrative. It should help forward the overall message of the video. It needs to be relevant to what’s being said.
Let’s say you’re planning a documentary which involves traveling across the United States and stopping in various cities to interview certain people on the same basic set of questions. One thing is for certain. You’re going to interview those people. That’s what you do know. But you’ve never been to these places and have no idea in advance what also should be shot in terms of B roll, so you’re going to ‘wing it’ and hope you’re covered.
Well actually, you already know more than that. You know you’re going to a particular city or town.
Most every city or town has a ‘Welcome to ___’ sign. Shoot it.
Mount your camera on the windshield or handhold it and shoot some traveling shots, highway signs, landmarks and anything of interest as you arrive. You may only wind up using one or two of those shots—or none—, but so what? You’re not doing anything but driving. (let me clarify that: If you’re alone, use a mount. If you’re with someone, have them hold the camera).
Shoot some establishment shots of the town and its landmarks. Long shots, medium shots, close shots, detail shots.
Shoot the bustling downtown–or the vacant one.
Shoot the exterior sign and buildings of the location you’re going to.
You know something else too. You know what the questions are and the subject material to be covered. So shoot stuff in that town that’s relevant to the subjects that will be discussed.
If relevant, shoot the interior of the establishment you’re going to. Not just long shots of interesting rooms, but detail shots of interesting details.
Yea, shoot atmospheric shots of flowers, trees, birds, lakes or whatever is there and may be relevant to what you’re doing.
And if it turns out you need a bird in flight for the Chicago edit and you didn’t shoot one, use the St. Louis bird you shot. Who will know? It’s called ‘cheating’ and Hollywood has always gotten a kick out of cheating.
If you spend an hour or two on the interview, spend that much or much more on the B roll.
After the interview you may realize you need to shoot something else based on what was discussed.
So shoot that.
You get the idea.
For a video to be interesting, it should not only have interesting narrative or story content, it should also be rich in story-telling pictures (footage). You won’t use a fraction of what you shoot, but you will have so much latitude in editing for having shot it that you will be free to make a great video no matter the headaches you may have endured during the interview itself.