For a comparison of the different headlight systems, the relative lighting power is judged on the basis of a circular paraboloid reference headlight of diameter 120 mm. For smaller sized lights the ellipsoid headlights have a clear advantage since their lighting power is independent of the headlight size. However if sufficient mounting space is available, then VF headlights with a starting diameter of approximately 170 mm are found to offer a better performance.
A further criterion for evaluation of headlights is the lighting width. This is the distance at which the density of light drops by 1 lux. In comparison to ellipsoid headlights the VF lights do not possess a higher lighting width and the frontal illumination is, however, homogeneous. Both these systems are clearly more efficient than conventional paraboloid headlights.