In short the default perspective view in Revit has a focal length of 38.6mm.
The following formula can be used to adjust the perspective field of view to the required focal length:
Field of View = DefaultFieldofView x 38.6/NewFocalLength
For example: Focal Length of 35mm
Field of View= 150mm x 38.6/35mm = 165mm
*Aspect ratio of standard film is 36x24mm or 3:2, thus Height = 2/3 x Width