Remember that when "zoomed all the way in" in the tank commander position (or any other non-optics gunnery position), it's actually a 1:1 representation of what you'd see in reality. Problem being most of us don't have virtual-reality-esque headsets to not need the FOV compression that you get before you "zoom."
This is not an accurate statement.
There are many issues when relating real life to a flat computer screen.
With optics the idea of zoom really doesn't make much since on a computer.
You can make an object larger (zoom in) just by moving your head closer to the screen.
Because of this simple fact you really can not say any give setting of zoom is what you would see in real life, because what you would see in real life is all defined by how far your eyes are from the monitor.
What we do in the tanks sights is make them all relative to each other with the same relative FOV (the black circle size) and ZOOM (how big objects are on the screen really the projection FOV) as the real world.
The amount zoom on the commanders position really depends on what your default FOV is in your graphic setup. But no matter what your (zoom out ) FOV is set at. When zoomed in your FOV is 25 degrees.
HiTech