According to [1], they collected half a million photos from instagram, selected 20,000-30,000 photos from each city from that, then filtered the set down by usi

According to [1], they collected half a million photos from instagram, selected 20,000-30,000 photos from each city from that, then filtered the set down by using Mechanical Turk. [1] http://selfiecity.net/#dataset http://selfiecity.net/#dataset