Controls manual focus during takes — records distances, handles focus charts, operates follow-focus wheels. Precision down to millimetres, especially on dolly and tracking shots.
The camera assistant — known in the English-speaking world as the Focus Puller or 1st AC — sits directly next to or behind the camera and controls the focus during the shot. This sounds like a routine task, but it's the opposite: while the director is thinking about composition and the cinematographer is planning the movement, the assistant has to calculate in real-time where the actor is moving and adjust the focus plane so finely that critical depth of field is never lost.
The classic method works with marks — the assistant measures the distance from the sensor to the actor's position before the shot, notes it on marking tape on the lens or on a dope sheet, and then, during the shot, turns the focus ring with sensitive precision. For dolly shots or tracking shots through a space, they have to calculate with the visual flow: an actor runs towards the camera — the distance shrinks from 3 meters to 0.5 meters. The assistant continuously adjusts, without jerking, without bumping. An error of 5 centimeters at wide apertures (1.4, 1.2) and a shot is unusable.
Follow focus systems — external focus controllers with motors and wireless control — have revolutionized this work in the last 15 years. The assistant still sits at the monitor or directly at the camera, but operates a thumb controller that tracks more precisely and smoothly than a hand on the lens ring. This is standard on large productions with digital cameras and complicated lighting situations. But even here: the assistant must anticipate, think along, read the director and the actor.
The responsibility is absolute. A blurry close-up of an emotional scene cannot be saved in the edit — it requires a reshoot or even a lost shooting day. Therefore, good camera assistants earn their place in the crew with serious craftsmanship. Experience, a steady hand, and a photographic memory for distances — that's the difference between a smooth shoot and frustration at the monitor.