The present invention relates to cameras.
In particular, the present invention relates to cameras of the type which are adapted to provide automatic determination of exposure time but which also are capable of being operated for manual selection of exposure time either in a mechanically determined range of exposures or in an electrically determined range of exposures.
Cameras of the above type control the duration during which the shutter is maintained open in an electrical manner by utilizing an electromagnet both during purely automatic determination of exposure time as well as during manual determination of exposure time in the manual-electrical mode of operation. Thus, primarily in connection with relatively long exposure times the electromagnet is utilized even during manual determination of exposure time while purely mechanical control of exposure time by way of a suitable mechanical timer is utilized for relatively short exposure times and bulb exposures. In this latter manner, manual control of exposure time is provided by with electrical or mechanical structures. The reason for this latter arrangement is that if it should be impossible to carry out electrical controls because the operator has neglected to load the battery into the camera or because the battery power has been consumed, then the most frequently utilized relatively short exposure times can be carried out in a normal purely mechanical manner, unless, of course, the brightness of the available light is too low. Furthermore, in the case of exceedingly long exposure times such as those utilizing bulb exposures, consumption of battery power can be avoided.
With an arrangement according to which manual control of exposure time both with electrical and mechanical structures are utilized, it would be possible to avoid wasteful battery power comsumption by linking the current-source switch to the exposure time setting dial in such a way as to disconnect this switch in the range where exposure time is controlled by the purely mechanical structure. Such an arrangement would be inconvenient, however, inasmuch as with disconnection of the current-source switch in the range where exposure time is determined mechanically the structure which measures the light and indicates the extent of illumination or desirable exposure time would have its meter also rendered inoperative, so that with disconnection of the current-source switch the automatic indication of exposure time also could be rendered inoperative.
USPTO Backgrounds
USPTO Backgrounds