How to check the hotel pinhole camera with Apple mobile phone?

When entering the room, first turn off the lights, close the curtains, keep absolute darkness, turn on the camera of the mobile phone, and scan carefully and slowly in every corner of the room. Once a bright spot appears on the dark mobile phone screen, it is likely to be a miniature camera.

Note that some Apple phones can't use this method, because their cameras have devices that filter red light.