Why does the camera has a little delay for motion detection recording?

There is a delay for the recordings because it takes about 3-4 seconds to wake up when it is triggered, before that, it is sleeping for saving power, that is why the battery can work for even more than 6 months, so when we understand how does it work, we should select a right installation position to make sure the camera has enough time to wake up and records the whole motion. The PIR sensor could detect motion from 15ft to 25ft, so please do not worry it can not be triggered, we should not install this camera as traditional continuous recording security cameras.