Page "Halogen lamp" Paragraph 13

For a fixed power and life, the luminous efficacy of all incandescent lamps is greatest at a particular design voltage.

Halogen lamps made for 12 to 24 volt operation have good light outputs, and the very compact filaments are particularly beneficial for optical control ( see picture ).

The range of MR-16 ( 50 mm diameter ) reflector lamps of 20 W to 50 W were originally conceived for the projection of 8 mm film, but are now widely used for display lighting and in the home.

More recently, wider beam versions are available designed for direct use on supply voltages of 120 or.