A-Roll vs. B-Roll: How to Use A-Roll and B-Roll Footage in Filmmaking

In video production, A-roll is the primary footage of a project’s main subject, while B-roll shots are supplemental footage. B-roll provides filmmakers with flexibility in the editing process and is often spliced together with A-roll footage to bolster the story, create dramatic tension, or further illustrate a point. Stories that rely entirely on A-roll footage might feel off-balance; this is why shooting B-roll is important.

The term “A-roll” is not longer used, but “B-roll” remains a common term in today's film industry.

Typical ways to use B-roll footage include:

• To establish the setting: If the primary footage does not directly reveal where a scene takes place, you can use B-roll to clarify the location. For example, if a scene begins inside a restaurant, the location of that restaurant might be unclear to viewers. In this case, a B-roll establishing shot could show the exterior of the restaurant to let the audience know where the scene takes place.
• To establish tone: B-roll can help set the tone or mood for the primary footage. For example, if a scene takes place at a house party, you could shoot B-roll of background characters dancing, playing drinking games, and socializing to help set the tone.
• To correct a scene’s pacing: B-roll footage can help you transition into or out of the primary footage. It can be jarring to cut directly from one scene to another, but inserting B-roll between scenes can slow down the pacing.
• As a cutaway: News programs and documentaries use B-roll video to cut away from the main news anchor or interview subject and provide visuals that help tell the story. This B-roll footage is often played with voiceover narration. For example, in a documentary about climate change, you could cut away from a talking head interview with a scientist to show B-roll footage of glaciers melting.
• To hide errors: Sometimes it's helpful to cut away from your primary footage to mask a continuity mistake. For example, maybe your main character in a scene is singing at a concert, but in post-production, you notice that a crew member was briefly visible in the shot. To cover up the mistake, you could cut to B-roll you filmed of the concert audience cheering.

On larger productions, A-Roll and B-Roll are commonly filmed by two separate film crews, first unit and second unit.

• The first unit crew films A-roll footage. The first unit is the larger of the two crews and is responsible for shooting the primary footage most important to driving the film's narrative. These scenes typically involve the lead actors and other actors with speaking roles. The director of a film stays with the first unit crew. They may shoot B-roll scenes if it makes logistical sense (for instance, if a necessary B-roll shot is at the same location where the first unit is already filming), but shooting A-roll is their central job.
• The second unit crew films B-roll footage. The second unit is the smaller film crew responsible for shooting all the extra footage not covered by the first unit. It’s the second unit director’s job to ensure that the B-roll footage blends flawlessly with the rest of the film. This means the second unit director often fills their shot list with camera movements and angles designed to match the style of the first unit director. In addition to shooting B-roll, second unit crews are commonly tasked with shooting action sequences that contain complex stunt work.

Smaller productions won't always have two film crew units; in these cases, the single main unit would also shoot B-roll. Depending on the needs of the production, stock footage can be a viable option for filmmakers looking for supplemental footage but unable to shoot original B-roll.

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