As more people choose to use an IdentiLynx camera for road or cross country without using a side camera to trigger when it captures image, knowing how to set the active area to avoid capturing extra image when no finishers are present is very important.
You can define a part of the image as the part you are watching for change of image so that when a participant passes, you capture their image. Essentially the camera becomes motion sensitive, but only in the defined area instead of over the entire image area. This method will also work with your side camera, but is less commonly an issue because you would typically shoot against a backer board.
Here is the white paper on this topic.
Time sequenced images
Visible bib numbers
Backs up a chip or manual system