In Koopman's photos alienation plays an important part. They show a preoccupied person with an attribute or object. For example, in one of the photos three stones take the place of the head, in another someone is hidden behind a vertical beam, on which maple leaves have been pinned at face height. Attribute and body melt into one, creating a whole new creature.

Other constants in Koopmans' work are minimal depth of field and frontality. He challenges his viewer to unravel the mystery of his photos.