Abstract: An adapter for mounting an instant picture cassette to a 35 mm camera, the back panel of which is removable, comprises an adapter plate which carries a back member corresponding to the back panel of the camera as well as an instant picture cassette. In an opening of the adapter plate a fiber optic face plate is mounted by means of a resilient support of silicone rubber in a position which ascertains its contacting the film guides of the camera which define the camera's focal plane. The resilient support of the face plate allows the same to adjust its position automatically when contacting said guides. The face plate transfers the picture from the image plane of the camera to the surface of the instant picture film so that an instant picture can be taken through the optics of the 35 mm camera which is useful for producing test pictures before taking pictures by means of the normal camera.