Standard resolutions -
On a widescreen monitor, this gives you the full FOV but leaves black bars at the sides.
https://i.imgur.com/Bz8wqWK.jpg
If you use a widescreen resolution, you get this FOV, it fills the screen, but the top and bottom are cropped -
https://i.imgur.com/sQuChkh.jpg
The blue box shows the cropped zone-
https://i.imgur.com/EPl5bO7.jpg