Shoot one frame every few seconds instead of twenty-four every second, then play the result back at normal rate. Processes far too slow to perceive — clouds crossing a valley, a flower opening, a city moving through dusk — become visible motion.
Interval choice is the core decision, and it depends entirely on subject speed. Fast clouds might need one or two seconds between frames; a construction project might need minutes or hours. The arithmetic is unforgiving: at one frame every two seconds, a ten-second clip at 24fps requires eight minutes of shooting, and a sunset sequence can mean hours on location.
Two problems dominate in practice. Flicker appears when auto exposure adjusts between frames, so manual exposure is standard — with the wrinkle that a dusk sequence genuinely needs exposure to change, handled by a technique called bulb ramping. And any camera movement between frames ruins the sequence, making a locked-off tripod essential.