If a camera registers an event and you want to know if and what other cameras in that camera group were recording at that time, you can use Grid Playback to view the recordings of multiple cameras synchronously.
The camera in the focus window is the lead camera. So, if you are browsing the recordings on this camera to find events or specific situations or if you are playing back recordings, the other cameras will follow the leading camera as soon as playback is paused. The program always shows the event images that are closest to the timestamp of the leading camera. If the time of the other cameras differs from the leading camera, the difference will be displayed at the lower border of the event images.
Hint: You can also use the Grid Playback by dragging a group onto the Playback view. The original camera will be shown in the focus window.