Off: sound or action outside frame—voice, footsteps, door slam. On: visible or audible within frame. Basic production notation for sound and editorial.
On set, we make a radical distinction between what the viewer sees and hears, and what happens behind the scenes. On means: the source of the sound or action is within the frame — the actress speaks, her lips move, we see her. The camera captures the source. Off is the opposite: the voice comes from outside the frame, the door slams shut behind the camera, footsteps approach from the left, but no one is visible. The source exists in the space, but not within our chosen frame.
This distinction is essential for sound and editing. In the script, we note "Off-voice" — for example, a police officer calling from outside the door while we see the suspect in a close-up. In the sound report, we differentiate between on-dialogue (filmed synchronously) and off-dialogue (dubbed later or voice-over). On set, this means concretely: for on-recordings, the sound mixer ensures the sound source is captured cleanly, without interference from behind. For off-sounds, we position the speaker or actor outside the frame and still record the sound. The camera operator needs to know the direction of the off-source to maintain the correct perspective.
In editing, this distinction becomes cinematically interesting. Off-dialogue can create emotional distance — the viewer hears someone but only sees reactions. An off-sound (footsteps, engine, phone) increases tension through the unknown. On-sound feels immediate, tangible, honest. In mixing, we differentiate accordingly: on-material remains spatially bound to the image, off-material can be processed more freely, with more reverb, more presence, or alienation.
Beginners often confuse off with voice-over — yet voice-over is only a special form of off, namely commentary or reflection. Simple off-dialogue (someone calling through a door) is far from being a voice-over. On set, this confusion leads to clean takes that cannot be edited later because the spatial consistency is incorrect. Therefore, before each shot, we clarify: What is on, what is off — and where is the source in space?