Global Shutter

A global shutter is a sensor design where every pixel starts and stops its exposure at the same moment. The charge from each pixel is held in a small storage cell and read out afterward. Because the whole frame captures one instant, fast-moving subjects keep their true shape and a flash can fire at any shutter speed. It is the opposite of a rolling shutter, which reads the sensor row by row.

A rolling shutter reads the sensor one row at a time, so the top of the frame is captured slightly earlier than the bottom. Fast motion or a fast camera pan can bend straight lines, and flickering lights can leave dark bands. A global shutter reads every pixel from the same instant, so there is no skew and no banding inside a frame. The trade is slightly less dynamic range and a higher base ISO.

The Sony A9 III, announced in late 2023, was the first full-frame mirrorless camera with a global shutter. Cinema cameras such as the RED Komodo and many industrial and machine-vision cameras also use one. Older CCD sensors in compact cameras worked the same way, which is why some early digital cameras could sync flash at 1/500 s. Most current mirrorless and DSLR bodies still use a rolling shutter with a mechanical shutter in front of it.

A mechanical shutter uses two curtains. Above about 1/250 s the second curtain starts closing before the first has fully opened, so only a moving slit of the sensor sees light at any moment, and a single flash burst lights only part of the frame. A global shutter has no curtains. The whole sensor is exposed at once for the chosen time, so one burst covers the full frame at 1/1000 s, 1/8000 s, or faster, with no need for high-speed sync.

Slightly. Each pixel needs a storage cell to hold its charge, which takes space from the light-gathering area. Cameras with a global shutter tend to have a higher base ISO, around 250 instead of 100, more noise in the shadows, and roughly one stop less dynamic range than a comparable conventional sensor. In good light or with flash the difference is hard to see. In a high-contrast landscape pulled hard in editing, it can show.

No. Motion blur comes from the subject moving while the shutter is open, and that depends on the exposure time. A global shutter only fixes skew, the bending that happens when different rows are captured at different moments. A hummingbird at 1/250 s still blurs on a global shutter camera. To freeze it, use a shutter speed of 1/2000 s or faster, or add a flash, whose short burst does the freezing.

It removes the bands. LED and fluorescent lights pulse many times a second, and a rolling shutter catches bright and dark phases on different rows, leaving stripes. A global shutter captures all rows at once, so each frame is evenly lit. The frame can still land on a dark phase and come out underexposed, and brightness can vary from shot to shot in a burst. A shutter speed of 1/100 s or slower covers a full cycle and evens it out.

No. Electronic shutter means the sensor itself times the exposure, with no mechanical curtains moving. Almost every electronic shutter in today's cameras is a rolling shutter, reading rows in sequence, which is why silent mode can bend fast motion and show banding. A global shutter is an electronic shutter that reads every pixel at once. So all global shutters are electronic, but few electronic shutters are global.

Close, but not exactly. At speeds below the sync speed, a mechanical shutter opens fully and the whole sensor sees light at the same time, which is why flash works there. But the curtains still take a few milliseconds to travel across the sensor, and above the sync speed they form a moving slit. Fast subjects can show slight skew even with a mechanical shutter. Only a true global shutter captures every pixel at the same instant at every speed.

Photographers who shoot fast action with flash or under tricky light gain the most: sports, motorsport, birds in flight, dance, and stage work. Anyone who wants silent shooting at high frame rates without bent lines also benefits. Landscape, portrait, and studio photographers give up some dynamic range for a feature they rarely use, so a conventional sensor with a mechanical shutter still serves them better and costs less.