I always sign up on the "My Plans" webpage for first night pics (where I get shore excursions, onboard fun and whatnot). On the ship, the receipt has shown a charge, then a credit for the amount charged (making it free). I was told on the phone with a CM to do it that way in order to get the free Pearl pics. Not sure if that's the only way, but it's been successful for us on many cruises now