Problem with camera in VR

I need to be able to change the FOV of a camera at runtime, and this camera is not rendering to the eye targets. The camera's target eye property is set to "None (Main Display)" in the editor. However, I am encountering this error when I try to modify this non-VR camera:

Cannot set field of view on camera with name 'Camera (main display)' while VR is enabled.

UnityEngine.Camera:set_fieldOfView(Camera, Single)

Why is changing the FOV forbidden for all cameras, just because one camera is in VR mode? Is this a bug?

P.S.: I should note that it is still possible to use Camera.CopyFrom() to modify the camera FOV when in VR mode.

 

hmm.. first, i don't know it is helpful.
i tried modify VR camera FOV, so finding how to change VR Camera FOV Value.
i'm using MRTK(Mixed Reality Tool Kit) , and 'using Holotoolkit.input.XR;'
- XRDevice.fovZoomfactor <- changing VR camera fov .
ex) XRDevice.fovZoomfactor = 2; <- scope 2x
I hope that it is helpful for you.