Ray used the camera while Peter Venkman was trying to communicate with the Library ghost. It is unclear if the camera was successful in photographing her, however from this research done during the Library Ghost encounter helped them to figure out how to capture and store ghosts. After they learned they got fired, Ray turned over the camera to one of the Removal Men.
Ray used his camera to photograph Peter Venkman holding the newly discovered Poveglian Artifact. He sent copies of the photos to Egon Spengler for a translation of the faint Swedish writing under the artifact's design.
The Leather case (also known as the Nikon FM2 FE2 FE Camera Leather Case) is also seen on Ray and is sometimes mistaken for another unknown prop.