Normally aiming sets your zoom to a fixed field of view regardless of your FOV settings.
In the unmodified game, this can make aiming zoom in way more then intended at high FOV settings, and in some cases aiming would even zoom you out, instead of in, with the lowest FOV setting.
With this mod, your screen will always be zoomed in/magnified by the same multiplier. If a scope enlarges your target by 3x with a Look FOV of 50, it will also enlarge your target by 3x with a Look FOV of 85. This is accomplished calculating a magnification value based on the default FOV of 65, and this magnification value is then applied to your Look FOV setting when aiming.
Known Bugs: If you modify your FOV in your graphics settings, your held weapon's zoom fov won't be updated until you switch off and back to it