The Outputs Tab: File Output
Checking the "Use file output" check box enables the controls in the "File" group box. The file output provides a periodic capture of the camere image, which is saved as a JPG in a directory of your choosing.
The "Image save folder" line edit is required for file output, and must specify a directory where you have write access. Clicking on the button to the right of the line edit will bring up a file dialog that starts you off in your home directory.
The "Seconds between saves" spin box allows you to specify the amount of time between each image save. MJPG-streamer doesn't have any limits on what this value can be; StreamMinder allows values from 0 to 8,640 seconds (365 days) in increments of 0.001 seconds. Clicking the up and down arrows on the spin box changes the value by 0.1 seconds.
As an option, you can have MJPG-streamer run a command each time an image is saved. This is handy for, e.g., sending the new image to your Web server via SFTP where ZoneMinder will pick it up. Note that you need to include the full path to the command in this line edit. In a terminal, you can use the "which" command (e.g., which sftp) to get the full path of any executable in your execution path.