One example of this was at a mosque in Quanzhou, China.

I had entered the prayer room, and knelt down to take a photograph of a courtyard.

A Japanese tour group soon after made it to the entry way of the prayer room, but stopped to take a picture of me, with the tour guide saying "oh, look, a Muslim is about to pray." I chuckled, and told her that I was also a (non-Muslim) tourist, to which she sheepishly laughed.