How to create a camera view from a perspective viewport

For a standard 3Ds camera, simply set the perspective view as you like and then hit Ctrl+C. 

A standard 3Ds camera will be automatically created, from your current perspective view.

For a VrayPhysicalCamera, you first have to create a VrayPhysicalCamera anywhere on the scene. It really doesn't matter where.

Switch to perspective view and set the view as you like. Then select the VrayPhysicalCamera (you can hit “H” and select it from the dialog) and with the camera selected, just hit Ctrl+C again, and the Vray camera will move automatically to match your perspective view. 

Note: If you notice that the new Camera view is slightly different from the perspective view, you just have to tweak the Camera’s Film Gate or Focal Length, in the Modify Panel.