Otherwise, your milage may vary. Set the camera to high, low or extended resolution mode. Time of taking a snapshot is included inside the JPEG files produced. Note that the models which display the time on the LCD will then display GMT rather than local time. With -z option, time shifted by the timezone offset is set, and the LCD will display local time.
Valid interval depends on the model.
Special speed value auto will set automatic shutter. Note that this only works while the camera always set automatically. Also note that there is no known way to control the aperture value from the host. Set the camera identifier string that is included inside the JPEG files produced. As far as I can tell, on fixed focus models macro only means force minimum aperture, not change the focal length.