I looked at the Apple’s website and noticed that they were giving focal lengths for each camera but no sensor size. On one of their camera they give the focal length and field of view. So I took my P-Cam app (a cinematographer app to do camera and lenses math) and for a camera to have a focal length of 13mm and a field of view of 120°, the sensor size should be about the size of film IMAX 65mm cinema camera. 13mm on a 35mm still camera would give an 80° field of view and you would need a 10.39mm lens to get to 120° and a 1mm focal length on a 1.4” sensor.
So how are they measuring those focal lengths?
Smartphone has different lens array design, so that calculator probably doesn’t apply to smartphone cameras.
This is the correct answer
The focal length is the distance of the film plan and the nodal point of the lens. The field of view is the angle you can see with a certain lens focal (nodal point distance) with a given observation surface (could be analog, digital, biological) Whether it’s celluloid, digital, stills video or phone or your eyes. All have the same physics and optics. This applies to any and all cameras.