Lens-end lamps are used for intensive lighting of small areas. The angle of opening of the light spot is smaller and the light intensity greater, as the filament becomes shorter. For this reason, lens-end lamps normally have a low rated voltage (<6 volt with filament C-6 or C-2R) and a high rated current. The light intensity in the direction of the lamp axis can be more than 5 times as large as for a similar lamp without lens.
If there are special requirements to the shape of light spot, the following specifications are necessary:
R = distance lens/test surface.
D = minimum diameter of the illuminated circle.
M = maximum extent of the illuminated area.