This subject of calculating camera variables manually has come up a couple of times before. This discussion may be of use to you.
You might want to check this information as well. It was taken from here https://github.com/IntelRealSense/librealsense/blob/master/doc/camera_specs.md.
--------- R200 F300 SR300 Indoor Range 0.7m – 3.5m 0.2m – 1.0m 0.2m – 1.5m Outdoor Range 10m NA NA Field of View 56°x43° 68°-54° 68°-54°
Hopefully this information will help you.