Is there any way to fine-tune the mouse sensitivity?

Solution 1:

From the PC Gaming Wiki, "BioShock Infinite - Mouse speed slider tweak" article:

Mouse slider tweak

This fix will modify in-game slider and give better control.

• Navigate to %USERPROFILE%\Documents\My Games\BioShock Infinite\XGame\Config\.
• Locate and open file XUserOptions in text editor (notepad for example).
• Locate lines MinMouseLookSensitivity=0.100000 and MaxMouseLookSensitivity=4.000000 and change values to your taste. Values 0.05 for MinMouse and 0.5 for MaxMouse works OK
• Start the game and set your desired sensitivity via slider.

Finer grained mouse sensitivity

This fix will let you set exact sensitivity values.

• Navigate to %USERPROFILE%\Documents\My Games\BioShock Infinite\XGame\Config\.
• Locate and open file XUserOptions in text editor.
• Locate line MouseLookSensitivity and set to desired value. This value has the same effect as the MouseSensitivity string used in other Unreal Engine titles.