Camera with shutter speed detection and correction

A camera comprising:

• an image sensor which photo-electrically converts an object image and outputs an image signal;
• a shutter which is placed in front of said image sensor and opens/closes by making a front curtain and a rear curtain travel;
• a light source which is placed in front of said shutter and illuminates said image sensor;
• a control unit which controls said image sensor, said shutter, and said light source so as to make the front curtain and the rear curtain travel with a predetermined time shift to form a slit-like opening between the front curtain and the rear curtain, and make said light source emit light a predetermined period of time after a start time of traveling of the front curtain and the rear curtain to expose said image sensor through the slit-like opening;
• a detection unit which detects a deviation between a position of an image of the slit-like opening captured by said image sensor and a predetermined reference position;
• a correction unit which corrects the traveling start timing of the front curtain and the traveling start timing of the rear curtain on the basis of the deviation detected by said detection unit;
• and
• a dust detection unit which detects dust adhered on a surface of an optical member which is arranged on a front surface of said image sensor or in front of said image sensor, based on an output signal which is output from said image sensor when said shutter is opened and said light source emits light,
• wherein said image sensor is exposed only when said light source emits light in a case that a detection operation of said detection unit is performed and said image sensor is exposed only when said light source emits light in a case that a dust detection operation of said dust detection unit is performed.