By default Day Z has a pretty narrow field of view that is not simple to change. However wildcard_ over at reddit has posted a good guide on how to increase your FOV.
1) Go to My Documents/ArmA 2/ and open up USERNAME.ArmA2OAProfile in notepad. Scroll to the very bottom and you’ll see two values, fovTop and fovLeft.
2) Calculate what vertical FoV corresponds to your desired horizontal FoV using this calculator. Make sure the “resolution” information is correct!
3) Take that number, go to Google, and search “X degrees in radians” to convert it. It should be a small number, between .5 and 1.5 in all likelihood. Round it off at the hundredths – I hear ArmA will chop off any digits after that anyway.
4) Enter that value as fovTop in notepad.
5) Using a calculator, divide that number by the second number in your aspect ratio – in my case, 16:10, so I divide it by 10. Then multiply it by the first number, in my case 16. Now enter that number for fovLeft, and round it the same way (leaving only 2 digits after the decimal point).
For the lazy people here are some values you can just copy paste.
1920 x 1080 at 90 FOV =
1680 x 1050 at 90 FOV =
2560×1600 at 90 FOV =