PLEASE READ THE WHOLE POST BEFORE YOU DO ANYTHING - this is so you understand what you're doing, thanks.
Goto the .../builds/release/ folder
Open up the file called "startup.ini" in notepad
Add a new line at the top by hitting return and add the command FOV xx where xx is equal to the FOV you want to use. once you're done your file should look something like this:
It's important the command goes before the [FileSystem] tag, also note that I picked 120 for experimental purposes and you will need to change the FOV to whatever you think is best, I will spend time soon working out what it should be set to for 16:10 monitors.fov 120
Now save that file and you can load Bioshock with that FOV
I am not exactly sure what the default FOV is but it's probably 85 or 90, so if you want to return back to another FOV you will have to change the file again and re-load
This allows you to change the horizontal FOV but NOT the vertical which is ideally what we'd need to change to fix this easily.
So what we have to do instead is change the resolution in game to something that has a 4:3 or 5:4 aspect ratio (this is for non widescreen CRT or LCD respectivly) so pick someting that has a smaller vertical resolution than your monitors native resolution (since this is the smaller of the 2)
Example: if you have a 1680x1050 monitor like me then 1280x1024 is close to the same vertical resolution while remaining smaller so it will fit and not need much stretching.
Your monitor will then stretch the 4:3 or 5:4 resoltion to fit the whole screen thus stretching the horizontal a lot, and this is what the larer FOV compensates for, it gives you a wider viewing angle to start with and so the final result looks normal, only you have a wider FOV and you keep the top and bottom parts of the screen.
I've been struggling to bind a key to get the console working so you can just open that but theres no documentation for switches for the executatble to enable it, nor what the keybind is called so we could do it in the startup.ini file.
Please note that this is workaround and you do it at your own risk, the worst that can happen is you set a stupid FOV and cant get it back or someting daft, in which case just uninstall/reinstall the demo.