The time lag between shutter release is the time between pressing the shutter button halfway to focus on the image and pressing it fully to begin the recording of the image. This delay or lag is the time it takes the camera to perform the different functions of taking a picture: focusing, calculating exposure, releasing the shutter, and recording the image to the memory card.
There are two primary specifications associated with shutter release time:
- Click-to-capture: The sum of all four elements above. It is the time from pressing the shutter release to the time the camera is ready to take the next picture (when not in a continuous shooting mode). This is often expressed in tenths of a second or can be as much as 1 second.
- Release lag: The time from when the shutter is fully depressed until the capture actually takes place. This is often expressed in milliseconds. A typical specification is 9 or 10 milliseconds.
- To shorten click-to-capture time, photographers often prefocus by half pressing the shutter button to lock the focus and exposure. With the shutter already half-pressed, only the release lag separates the full pressing of the shutter release and capturing the moment.
- Refer to the How long is the time lag between shutter releases? article for more detail and specific timing information.