Rolling Shutter

Rolling shutter is a readout method where the sensor captures the image one row at a time from top to bottom instead of all at once. Each row is exposed for the same length of time, but the rows start at slightly different moments. If the subject or the camera moves during that readout, straight lines lean and fast-moving parts bend. Almost every CMOS sensor works this way, and the effect is strongest in electronic shutter mode.

Vertical lines lean when the camera pans fast, so buildings and lamp posts tilt sideways. Spinning or flapping objects such as propellers, fan blades, and bird wings come out curved or broken into pieces. Under LED or fluorescent light, dark horizontal bands cross the frame. In video the whole image wobbles like jelly when the camera shakes, which is why the artifact is sometimes called jello.

A rolling shutter reads the sensor row by row, so different parts of the frame are captured at slightly different times. A global shutter exposes and stores every pixel at the same instant, so there is no skew and no banding inside a frame. Global shutter sensors cost more and give up some dynamic range and a stop of base ISO, so most cameras still use rolling shutter and rely on fast readout or a mechanical shutter to hide it.

Slightly. Two curtains travel across the sensor in a few milliseconds, so the top and bottom of the frame are still exposed at slightly different times. For almost every subject that gap is too short to see. A propeller at full speed or a golf club at impact can show mild bending, but a cyclist, a runner, or a bird in flight comes out straight. That is why the mechanical shutter remains the safe choice for action.

LED and fluorescent lamps switch on and off many times a second, usually 100 or 120 times. A rolling shutter reads the sensor over a longer period than one of those cycles, so some rows are captured during a bright phase and others during a dark phase. The result is horizontal stripes of different brightness. A shutter speed of 1/100 s or slower covers at least one full cycle per row and evens the bands out.

Switch to the mechanical shutter or electronic first curtain for fast subjects and fast pans. Pan smoothly and keep the subject centered so its rows stay aligned. Under artificial light, turn on the anti-flicker setting or drop to 1/100 s. If the camera has a stacked sensor, its electronic shutter is fast enough for most action. For the rare job where none of that is enough, a global shutter camera removes the problem entirely.

Readout speed is how long the sensor takes to read every row of one frame. A typical non-stacked full-frame sensor needs around 1/15 to 1/30 s in electronic shutter mode. Stacked sensors read in about 1/250 s, and the fastest in under 1/300 s. The shorter the readout, the less a subject can move between the first row and the last, so the less skew appears. Reviews and spec sheets list the figure in milliseconds or as a fraction of a second.

A flash burst lasts about 1/1000 s or less. With a slow rolling readout, only the rows being read during that burst receive the light, and the rest of the frame stays dark or shows a bright band. Many cameras disable flash in electronic shutter mode for this reason. Cameras with fast stacked sensors allow flash with the electronic shutter at low sync speeds, and a global shutter camera can sync at any speed.

Yes. Video records 24 to 60 frames every second, so the camera is almost always in electronic shutter mode with the full readout time exposed. Quick pans, handheld shake, and vibration from a car or drone make the frame wobble, the jello effect. Photographers see rolling shutter only in the single frame they keep, and they can switch to a mechanical shutter. Videographers rely on fast readout, stabilization, and slower camera moves instead.

Yes. Some photographers twist or sweep the camera during a slow electronic shutter exposure so trees, lights, and skylines stretch into curved streaks. Shooting from a moving train or car with a phone gives the same bending to foreground poles and fences. The results look nothing like ordinary motion blur because the distortion follows the readout, not the exposure time. It takes practice, but the effect is impossible to fake convincingly in editing.