An electronic device (200 or 300) comprising: communication means (402 or 318) configured to communicate with an image pickup apparatus (100 or 300); first measurement means (202a or 311a) that measures a time related to an operation of the electronic device; state change means (202 or 311) configured to change an operation state of the electronic device (200 or 300) to an activation state in which an operation corresponding to an image pickup of a subject by the image pickup apparatus (100 or 300) can be performed and a power saving state in which power consumption is lower than power consumption in the activation state; and timing calculation means (202 or 311) for calculating an activation timing for starting an operation for changing the operation state of the electronic device (200 or 300) from the power saving state to the activation state by the state change means (202 or 311), wherein, in a case where the electronic device (200 or 300) receives from the image pickup apparatus (100 or 300) via the communication means (402 or 318) information related to a timing for picking up an image of the subject by the image pickup apparatus (100 or 300), the timing calculation means (202 or 311) is configured to calculate (S203, S204) the activation timing on the basis of the information related to the timing for picking up the image of the subject, wherein the state change means (202 or 311) is configured to start the operation for changing the operation state of the electronic device (200 or 300) from the activation state to the power saving state after the activation timing is calculated by the timing calculation means (202 or 311), and wherein the state change means (202 or 311) is configured to start the operation for changing the operation state of the electronic device (200 or 300) from the power saving state to the activation state in response to the time measured by the first measurement means (202a or 311a) having reached the activation timing without reception of an activation instruction from the image pickup apparatus (100 or 300) via the communication means (402 or 318), said activation instruction being a signal for instructing the electronic device to start the operation for changing the operation state of the electronic device from the power saving state to the activation state. communication means (402 or 318) configured to communicate with an image pickup apparatus (100 or 300); first measurement means (202a or 311a) that measures a time related to an operation of the electronic device; state change means (202 or 311) configured to change an operation state of the electronic device (200 or 300) to an activation state in which an operation corresponding to an image pickup of a subject by the image pickup apparatus (100 or 300) can be performed and a power saving state in which power consumption is lower than power consumption in the activation state; and timing calculation means (202 or 311) for calculating an activation timing for starting an operation for changing the operation state of the electronic device (200 or 300) from the power saving state to the activation state by the state change means (202 or 311), wherein, in a case where the electronic device (200 or 300) receives from the image pickup apparatus (100 or 300) via the communication means (402 or 318) information related to a timing for picking up an image of the subject by the image pickup apparatus (100 or 300), the timing calculation means (202 or 311) is configured to calculate (S203, S204) the activation timing on the basis of the information related to the timing for picking up the image of the subject, wherein the state change means (202 or 311) is configured to start the operation for changing the operation state of the electronic device (200 or 300) from the activation state to the power saving state after the activation timing is calculated by the timing calculation means (202 or 311), and wherein the state change means (202 or 311) is configured to start the operation for changing the operation state of the electronic device (200 or 300) from the power saving state to the activation state in response to the time measured by the first measurement means (202a or 311a) having reached the activation timing without reception of an activation instruction from the image pickup apparatus (100 or 300) via the communication means (402 or 318), said activation instruction being a signal for instructing the electronic device to start the operation for changing the operation state of the electronic device from the power saving state to the activation state.