A lot of coincidence in photography comes from a point of view: yours
Coincidence is often (you might say even usually) in the eye of the beholder. This is what gives it a creative edge, because you’re basically saying to the viewer ‘I made this connection, and it’s not all that obvious, but I’d like to share it with you’.
Point of view has a double meaning here. There’s the mechanical point of view, which is how you position yourself for a viewpoint that points out the coincidence, together with the focal length, what you cut out of the frame, whether you get both things sharply focused, and so on. Then there’s point of view in the sense of your opinion: what you actually think about the juxtaposition of things. I’ve chosen this shot deliberately for being a bit borderline, tentative. I saw a coincidence, but not everyone will, and some might think it’s not a connection even worth making. In some ways, finding your own coincidences is like telling a joke. If it’s too obvious it’s just not funny. If the audience don’t get it because it’s too obscure, it’s really not funny. Visual coincidences in photography work best when they just hit the right spot. If you make a habit of looking for coincidences, and shooting whatever you can find, you can be sure that some will fall flat, and also that they depend on the individual viewer.
Another thing that visual coincidences have in common with telling jokes is that you can never explain them. If you need to, you already lost, so move on to the next shot. Be careful what you say in the caption.
A visual coincidence of shape and position in a small street in Cartagena, Colombia. Murals and graffiti make an easy starting point