Large format, still picture cameras that use films having a backing paper, are widely used. Some of these cameras are used in connection with film magazines that can be detachably mounted thereon. Such cameras are advantageous in applications where it is necessary to interchange different types of films, such as film for use in daylight, tungsten films, color films, monochromatic films and the like. For using different types of films interchangeably, a plurality of film magazines containing the different types of films is required, which magazines are selectively mounted on the camera depending on the type of photographs it is desired to take. Interchangeable film magazines of this type that have been recently developed and are now on the market incorporate motor-driven film wind-up mechanisms for easier and improved operation. The motor-driven film wind-up mechanism is electrically coupled to a controller in the camera body by mounting the film magazine on the camera body whereafter it can be operated by electric signals issuing from the controller in the camera body.
The above-described interchangeable film magazine is generally provided with a light-shielding plate made of opaque material, in order to prevent a film loaded therein from being exposed to ambient light when the magazine is detached from the camera. The light-shielding plate is adapted to be inserted into the film magazine to cover an exposure aperture formed in a front wall of the film magazine in a light-tight fashion, and to be removed before making exposures.
After the film is loaded in the film magazine, the magazine is mounted on the camera, and the light-shielding plate is removed from the magazine, the camera is not yet ready for making exposures; this is because an excess leading end portion of the film's backing paper covers the exposure aperture. For this reason, it is necessary to wind up the leading end of the backing paper to advance a photosensitive section of the film in alignment with the exposure aperture, before making exposures. Winding of the backing paper leading end has previously been effected by first aligning a mark on the back surface of the backing paper leading end with an index mark at a particular position on the inside of the film magazine. The back cover of the film magazine is then closed, and the loaded film is advanced a predetermined length prior to making the first exposure. This preliminary film wind-up operation may be performed manually by manipulating a film wind-up handle or by manipulating a button that causes a motor to rotate, if the film magazine is equipped with a motor-driven film wind-up mechanism.
An attendant disadvantage of such film magazines is the index-mark alignment operation. When the index-mark alignment is inexact, the photosensitive section of the film will not be accurately advanced, that is, it will be advanced too much or too little relative to the magazine exposure aperture. Precise index-mark alignment is therefore essential every time a new film is loaded in any film magazine, and this is a time-consuming and troublesome operation. Furthermore, when using the interchangeable film magazines, it is necessary to confirm whether the film magazine to be used has been properly loaded and is ready for making exposures, without removing the light-shielding plate therefrom. Such confirmation is also troublesome, and sometimes it is not done at all, especially where a plurality of film magazines are interchanged frequently.
USPTO Backgrounds
USPTO Backgrounds