Today’s Question: I just saw an announcement about a new Sony camera with a “global shutter”. They say it provides faster performance and no motion distortion, but what exactly is a “global shutter”?
Tim’s Quick Answer: A global shutter records data for the entire image sensor simultaneously, rather than row by row as is common with a rolling shutter. A global shutter prevents various distortion issues, such as motion distortion or flash distortion. The new Sony a9 III (https://bhpho.to/3FP2f3B) is the first mirrorless camera to feature a global shutter.
More Detail: Many digital cameras use a rolling shutter, in which image data is not gathered all at once. Instead, with a rolling shutter the image data will be captured by the image sensor row by row or column by column. While the data for the full sensor is read quickly, it isn’t read simultaneously, which can lead to problems with fast-moving subjects.
For example, if you photograph a propeller-driven airplane or helicopter, with a rolling shutter the blades can be significantly distorted because the blade was moving faster than the data was being read from the sensor. Similarly, flash photography can be a challenge with a rolling sensor, leading to issues where for example the top part of the photo might reflect the flash illumination while the bottom half is extremely dark.
A global shutter prevents these issues because all sensor data is recorded simultaneously. This provides exceptional performance with high-speed subjects and other challenging scenarios. The Sony a9 III (https://bhpho.to/3FP2f3B), for example, is capable of continuously shooting raw captures at 120 frames per second, and supports flash synchronization all the way up to the maximum shutter speed of 1/80,000th of a second.