Apart of your new Rotom Pokedex is the Poke Finder, a camera attachment that allows you to take photos of Pokemon at designated spots across The Alola Region. This feature is first unlocked when you reach the Hau'oli Cty Tourist Center. The mechanics are quite simple, merely by using your 3DS's Gyroscope to adjust before taking the perfect picture. You can even save photos from each session onto your SD Card to further share on social outlets. (You will even have an Island Trial that requires you to use Poke Finder.)
After taking a photo at any of these Poke Finder Locations, you can get is analyzed. This is a comment system where various NPCs will comments on your photo, sometimes will relevant advice and sometimes with nonsensical remarks. After the exchange, you will then get points by your Rotom Pokedex on just how good your Photo was. These points are higher depending on a number of factors: how rare the Pokémon is, how close you are to the Pokémon, the position of the Pokémon, and the Pokemon's pose. The better these factors are, the more points you will receive.
As you stockpile more and more points, you will actually receive more features based on the points required for such, often used to take better quality photos. After reaching 1,500 Points, you will receive the Zoom Feature on your Poke Finder. After reaching 10,000 Points, you will receive the Enhanced Zoom Feature. After reaching 100,000 Points, you will receive the Max Zoom Feature. And after reaching 1,500,000 Points, you will receive a Stamp in your Trainer Passport and will be able to call these Pokemon closer to you when taking Photos of them.