It depends on the situation and person, of course. However, it would be as follows: すみません。写真を撮らせてもらえますか？／Sumimasen. Shashin wo torasete moraemasuka? (Excuse me. May I take a picture of you?) すみません。一緒に写真を撮らせてもらえますか？／Sumimasen. Isshoni shashin wo torasete moraemasuka? (Excuse me. May I take a picture of you with me?) I hope it helps.

すみません, 一緒に写真をとってもいいですか？ sumimasen~ issho ni shashin wo tottemo ii desu ka? Excuse me, can we take a photo together? Saying it like this is more friendly, more kind of saying if it's okay to take a photo together. すみません、あなたの写真をとってもいいんですか？ Sumimasen, anata no shashin wo totemo iin desu ka? Excuse me, can I take a photo of you? 一緒 - together 写真 - photo とって - take いい - good/ okay ですか - is it? あなたの - your