1. Field of the Invention
The present invention relates to an exposure control apparatus of a camera having a plurality of exposure modes.
2. Description of Related Art
In a conventional camera having a plurality of exposure modes, a photographer can select a desired exposure mode by actuating an associated switch or button etc.
In a recent camera having modes other khan the exposure modes, such as a continuous shot mode, etc., mode selection is effected by activating a plurality of switches in combination.
However, ordinary photographers do not often use all of the various exposure modes, but rather use only a few specific exposure modes. Therefore, for the ordinary photographer, the need to activate several switches in combination to effect a mode selection is troublesome and complicated. A photographer is therefore prevented from easily setting a desired exposure mode.
Furthermore, in a program exposure mode of a known camera, a shutter speed and a diaphragm value are automatically determined in a specific, interdependent relationship. Accordingly, a photographer cannot vary the shutter speed and diaphragm values outside of this predetermined relationship.
When a known program shift mode is actuated in a program exposure mode, the shutter speed and the diaphragm value are always varied together while maintaining the predetermined relationship. Namely, it is impossible to vary only one of either the shutter speed or the diaphragm value in the program exposure mode, in a known exposure control system.
Therefore, in a conventional camera, if a photographer wants to vary only one of the shutter speed and the diaphragm value in the program exposure mode, it is necessary for him or her to troublesomely switch the program exposure mode to a shutter speed priority (EE) automatic exposure mode or a diaphragm priority (ES) automatic exposure mode.
In the prior art, the accuracy of the APEX values of the shutter speed and the diaphragm value was generally a 4/8 (1/2) step at the manual setting and 1/8 step at the automatic setting, respectively. Namely, the accuracy of a manual setting is lower than that of a automatic setting. Furthermore, the shutter speed Tv, and the diaphragm value Av which can be manually set, are values on an arithmetic progression having a difference of 1/2, such as 10/8, 14/8, 20/8, . . . , i.e., mixed numbers (which will be referred to as manual series values hereinafter) having an antilogarithm portion represented by 0/2 or 1/2. On the other hand, the shutter speed Tv and the diaphragm value Av, which can be automatically set, are values on an arithmetic progression having a difference of 1/8, such as 10/8, 11/8, 12/8, 13/8, . . . , i.e., mixed numbers (which will be referred to as auto series values or oputimum value hereinafter) having an antilogarithm portion represented by 0/8, 1/8, 2/8 . . . 7/8. Consequently, upon a manual setting, it is impossible to obtain values other than the manual series values which can be set in the automatic setting, such as 11/8, 12/8, etc. In addition to the foregoing, the accuracy of a exposure value Ev and the exposure values which can be set at the manual setting are 1/2 Ev and the manual series values at the manual exposure mode and 1/8 Ev and the auto series values at the automatic exposure mode and the program exposure mode, respectively.
The primary object of the present invention is to eliminate the above-mentioned drawbacks of a known exposure control system, having a plurality of exposure modes including program, shutter priority, diaphragm priority and bulb exposure modes etc., by providing a simple exposure control apparatus in which the exposure modes can be easily changed and a photographer can easily set optional exposure factors.