I don't know... but sometimes I think Using resolution 1028x724 (4:3) give you more to see on your back. Why?
maybe default is widescreen and using a 4:3 resolution increased the vertical fov rather than the other way around
Because it's a horiztontal-locked FOV. It's otherwise known as "vert-", meaning that as you go to a wider horizontal aspect ratio, you lose vertical FOV. The preferred method these days is "hor+", meaning that the FOV is locked vertically and you gain horizontal FOV as you move to a wider aspect ratio it's the same reason you can't use an eyefinity (multiple monitor) setup. Well, you can, but it would be like looking through a really narrow slit in a helmet because you would lose almost all vertical FOV I actually run the game at 1280x1050 with black bars on the side of my widescreen monitor just to get a better FOV I wish they would just make it customizable. It's dumb to force a PC game to use the same FOV as a console version. A PC monitor up close generally takes up a wider arc of your vision than a TV (even a big one) while sitting at a reasonable distance, so a PC version requires a wider FOV to feel natural.
