Patent US 3,958,261

A compact folding camera and viewing device and an apertured flexible mask removably attachable to the viewing device over the eye lens thereof. The mask folds flat within the viewing device in a storage position and when the viewing device is erected to a viewing position the aperture is positioned proximate the exit pupil of the viewing device and is oriented to cause a user to place his eye proximate the exit pupil and sight along the optical axis of the viewing device. The mask is provided with an antireflective face and the aperture is larger than the exit pupil so as not to restrict the field of view through the viewing device.