Mantle, d.p. on director Danny Boyle’s “Slumdog Millionaire,” also photographed 2007’s “The Last King of Scotland” for helmer Kevin Macdonald. Mantle previously worked with Boyle on “28 Days Later” and “Millions.” To shoot unobtrusively in the streets and slums of Mumbai, the Brit eschewed 35mm film cameras for smaller digital gear. “Physically it was very hard. I’m fit and strong but had to run like hell” during the shoots, Mantle says. “I can’t stand looking down at people, so I pulled the camera low so I was down with the kids.