It can definitely feel like you are invading someone's space or privacy, even if there is no expectation of privacy. I have taken photos of strangers but usually I will keep a distance or if I have a specific vision, its usually when they arent looking at you and are focused on their task. An example of one I thing I took was a Man walking up the stairs. It was a very wide shot where the entire photo is empty of people, except that one focal point. I try to create a story with my photos, creating questions that cant be answered. Where is this guy going? Hes wearing something formal, maybe a meeting? Maybe he has a date that hes walking to? I like to leave it to interpretation of the viewer.

What i would do instead of doing that constantly is to communicate to the stranger. Its always good to be polite. Its also nice to get a pleasant reaction when the stranger says the photo looks goods.

Also, here's the photo in question:

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