How do you unlock silver prints in Pokemon platinum?

1. Defeat the Elite Four and Champion Cynthia. This is the main objective of the game, and once you've accomplished it, you'll be able to access new areas and features, including the ability to unlock Silver Prints.

2. Talk to the woman in the Pokémon Center in Eterna City. She will give you a Photo Album, which will allow you to view and collect Silver Prints.

3. Catch Pokémon that have been photographed by the Pokétch's Photo App. When you catch a Pokémon that has been photographed, you'll receive a Silver Print. You can see which Pokémon have been photographed by looking at the Pokétch's Photodex.

4. Collect 50 Silver Prints. Once you've collected 50 Silver Prints, you'll be able to trade them in for a variety of items, including TMs, Berries, and even Legendary Pokémon.

5. Trade your Silver Prints with the man in the Battle Zone. He will give you various rewards in exchange for your Silver Prints, including TMs, Rare Candies, and even the ability to battle Legendary Pokémon.