Image pickup apparatus

1. An image pickup apparatus comprising:

a first image sensor configured to perform imaging;

at least one processor and a memory coupled to the at least one processor, the memory having instructions that, when executed by the processor, perform operations as a control unit configured to perform precapture imaging, when acquiring a first imaging instruction, to cause the first image sensor to repeatedly perform imaging, and causes the first image sensor to perform main imaging when acquiring a second imaging instruction during the precapture imaging; and

a first detecting unit configured to detect a change in a main object to be focused, and to output information about the change in the main object,

wherein the control unit changes control in the precapture imaging using the information about the change in the main object.

2. The image pickup apparatus according to claim 1 , further comprising:

a first recording unit configured to temporarily record an image acquired by the precapture imaging when the control unit acquires the first imaging instruction; and

a second recording unit configured to record the image acquired by the precapture imaging and an image acquired by the main imaging when the control unit acquires the second imaging instruction.

3. The image pickup apparatus according to claim 1 , further comprising an operation unit configured to output the first imaging instruction in response to a first-stage pressing operation, and outputs the second imaging instruction in response to a second-stage pressing operation.

4. The image pickup apparatus according to claim 1 , wherein the first detecting unit outputs to the control unit information about a pixel included in the first image sensor where luminance has changed as the information about the change in the main object when the luminance has changed in the pixel, and

wherein the control unit outputs a first control instruction to the first image sensor so as to transfer the first image sensor to a first state in a case where the control unit acquires the information about the pixel, and outputs a second control instruction to the first image sensor so as to transfer the first image sensor to a second state in which power consumption is smaller than that of the first state in a case where the control unit does not acquire the information about the pixel.

5. The image pickup apparatus according to claim 1 , wherein the first detecting unit includes a second image sensor different from the first image sensor, and configured to output information about detection of an entry of the main object into a detecting range as the information about the change in the main object when detecting that the main object has entered the detecting range of the second image sensor, and

wherein in a case where the control unit acquires the information about the detection of the entry of the main object into the detecting range, the control unit outputs a first control instruction to the first image sensor to transfer the first image sensor to a first state, and in a case where the control unit does not acquire the information about the detection of the entry of the main object into the detecting range, the control unit outputs a second control instruction to the first image sensor to transfer the first image sensor to a second state in which power consumption of the first image sensor is lower than that of the first state.

6. The image pickup apparatus according to claim 5 , further comprising a second detecting unit configured to output to the control unit information for detecting whether a photographer is facing the image pickup apparatus,

wherein the control unit changes at least one of a detecting range and a frame rate of the first detecting unit using the information from the second detecting unit.

7. The image pickup apparatus according to claim 4 , further comprising:

a second detecting unit configured to output to the control unit information for detecting whether a photographer is facing the image pickup apparatus; and

a notification unit configured to notify the photographer of information indicating that the main object has changed in a case where the control unit outputs the first control instruction to the first image sensor and it is determined based on the information from the second detecting unit that the photographer is not facing the image pickup apparatus.

8. The image pickup apparatus according to claim 1 , wherein the control unit stops the precapture imaging when determining that the main object has not changed, and resumes the precapture imaging when determining that the main object has changed after the precapture imaging is stopped.

9. The image pickup apparatus according to claim 8 , wherein the control unit deletes all images acquired in the precapture imaging a predetermined time after the first image sensor stopped the precapture imaging.