As Emma Watson told EW, the line between her public and private lives is necessary for stability. Part of that involves fan photos.

During a recent interview with Vanity Fair, the Beauty and the Beast star explained she rarely poses for snapshots because “it’s the difference between being able to have a life and not.”

“If someone takes a photograph of me and posts it, within two seconds they’ve created a marker of exactly where I am within 10 meters,” Watson said. “They can see what I’m wearing and who I’m with. I just can’t give that tracking data.” Instead, she offers an alternative, like an autograph or a conversation with a fan. “I’ll say, ‘I will sit here and answer every single Harry Potter fandom question you have but I just can’t do a picture.'”

However, the rule doesn’t always apply: “When am I a celebrity sighting versus when am I going to make someone’s freakin’ week? Children I don’t say no to, for example.”

Unlike other celebrities who grew up in the Hollywood spotlight, Watson was announced for the Harry Potter movies at the age of 10, and soon the age of social media would begin. “People will say to me, ‘Have you spoken to Jodie Foster or Natalie Portman? They would have great advice for you on how to grow up in the limelight,'” she recalled. “I’m not saying it was in any way easy on them, but with social media, it’s a whole new world. They’ve both said technology has changed the game.”

Plus, Potter-heads are part of a more intense breed of fandom. “I have met fans that have my face tattooed on their body. I’ve met people who used the Harry Potter books to get through cancer. I don’t know how to explain it, but the Harry Potter phenomenon steps into a different zone,” she said. “It crosses into obsession. A big part of me coming to terms with it was accepting that this is not your average circumstances.”

Related: Watch Emma Watson in the Latest 'Beauty and the Beast' Trailer