Arc Left

The camera swings to the left around the subject, so the background travels right behind them. The subject holds still and their world turns, which is a strong way to show somebody fixed in place while things change around them.

Direction matters when the arc has to join other shots. Curving left keeps the geography consistent with a scene that has been moving left, and breaks it if the scene has not.

The camera follows a curved path to its left at a constant distance from the subject. The subject stays centred, and the background sweeps in the opposite direction to the camera.

Background direction is the reliable way to lock this in. Say the background sweeps right, because that is what an arc left actually looks like, and it leaves no room for the model to guess.

Keep the radius steady. If the distance changes during the move, the arc turns into a spiral and the subject grows or shrinks as it goes.

Use it to match a leftward move already running in a scene, and to reveal what is on the subject's right hand side without them turning.

Drop the direction if the scene does not care. A plain arc with a named end frame is easier to get right.

A 360 degree orbit keeps going until it closes the circle. Arc Left stops part way, which is what lets it land on a composed frame.

The closing test applies. If the background returns to where it started, the model gave you an orbit rather than an arc.

The model tracks straight instead of curving, and the subject drifts out of centre. Say the path curves and the subject stays centred for the whole move.

The other failure is the arc going the wrong way, because left is ambiguous. Name the background direction, which is right for an arc left, and the ambiguity disappears.