The minigame lets the main character pretend to be a professional photographer while the subject in front of the camera is taking suggestive poses. As of version 0.20.5, only two characters can serve as models: Jenny in her route; and Roz, the hospital receptionist, after having made enough progress in Diane’s route.
It’s as easy as pressing the camera icon. No focus or framing has to be done.
In addition to unlocking the next steps of the routes, the photos taken are part of the official Summertime Saga wallpapers.