Abstract: A device for indicating the depth of field of a camera having aperture setting means and range setting means. The device comprises a plurality of optically active elements positioned for view in the camera viewfinder and scale means associated with the optically active elements. Means are also provided which are responsive to the camera aperture setting and the range setting to select adjacent ones of the optically active elements to indicate the depth of field.

Abstract: The angular distribution of illumination passing through a selectively diffusing element can be varied by placing the diffusing element in a reflector unit so that the diffusing element is in the path between a light source and the object to be illuminated. A variable diffuser can comprise a liquid-crystal cell driven by a variable voltage to control the amount of diffusion by the reflector unit. The control voltage can be set in accordance with change in focal length in a zoom lens of a camera using the light source and reflector unit as a flash gun.

Abstract: A focusing screen of a viewfinder system for a photographic camera is designed as a liquid crystal cell having two transparent bodies which lie opposite one another with plane surfaces at a short distance from each other, these plane surfaces carrying electrodes. By applying a current to the electrodes, or by cutting off such current, the character of the focusing screen is changed, providing a single multi-purpose screen and obviating the need to change the screen when focusing for a different type of photography. The liquid crystal screen may be used in conjunction with or may be formed as part of a field lens or a Fresnel lens forming part of the viewfinder system. Various arrangements of the electrodes for changing the character of the screen over only part of the area thereof, rather than the entire area thereof, are disclosed.