The “fix bit rate” and “fix quality” options on the “Video” settings page are ideal for this purpose. “fix quality” ensures that the video will not change quality for any reason, and therefore a lower quality will yield less bandwidth usage. If you would like a strict limit on the bandwidth usage of the camera, the “fix bit rate” option is the best choice as it will be a strict upper bound on the transfer rate of the camera, but may result in inconsistent image quality.