〜てもらえませんか・〜ていただけませんか

てください is polite, but it's still an instruction. To ask a real favour, Japanese turns it into a question, and a negative question is softer still:

• 撮ってくれませんか: could you take it?
• 撮ってもらえませんか: could I get you to take it?
• 撮ってくださいませんか: more respectful
• 撮っていただけませんか: the most polite, for strangers, bosses and customers

Between friends: 撮ってくれない?

The more polite versions are longer, and that's the point. Asking a stranger for help with てもらえませんか is a safe everyday choice; save ていただけませんか for when you want to be especially careful.