| 摘要 |
PURPOSE:To prevent the deterioration of the focus detection accuracy, and the generation of a large focal misalignment, by detecting whether a vignette of an entrance pupil exists in an AF system or not by comparing a substantially F-number and a critical F-number, and deciding whether a focus detecting operation is inhibited or allowed. CONSTITUTION:A substantial F-number converter 29 converts the shift quantity from a shift encoder 25 provided on a shift mechanism 24 of a shift lens 21 to a substantial F-number Fs, and outputs it to a comparing circuit 35 of a camera main body side. The comparing circuit 35 compares the obtained substantial F-number Fs with a critical F-number Fl which is read out of a critical F-number memory 34, and only when Fs<=Fl holds, an AF operation of an arithmetic control circuit 31 is allowed. When Fs<=Fl does not hold, that is, when a pupil vignette exits, the comparing circuit 35 inhibits the AF operation of the arithmetic control circuit 31. In such a way, it can be prevented that a focus detecting operation is executed carelessly, and the deterioration of the focus detection accuracy and a large focal misalignment are generated. |
