The Plano Convex
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The Plano Convex or PC spotlight is one of the earliest form of
theatre spotlight and used as a lens. Consists of a simple ‘box’
housing which contains a lamp and reflector behind a plano
convex lens. Usually the modern units range from 300 to nearly
2000 watts while the lens diameters include a 5”, 6” and 8”
width. The beam disperse varies from 10 to 65 degrees in a
single fixture.
Though developed as a replacement for the incandescent lamp
during the early 1880s, but was replaced with the ellipsoidal
reflector fixture in the 1930s.However, the plano convex
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fixture is still manufactured and are simple in operation and construction.
The fixture provides a circular beam with a defined outer edge but the field of
light or the distribution of light across the beam is uneven. Many optical
aberrations are seen like rainbow effects at the edge of the beam.
Lamp and the reflector are mounted in unison and move in all positions namely
forward and backwards with relation to the lens. Moving towards the lens expands
the beam in size and as the lamp and reflector move away the beam shrinks in
size or narrows.
The usual applications of a plano convex spotlights are useful in lighting up
the acting area and providing local lighting to a specified area on the stage.
However, there are no beam controls available like shutters, iris and barn
doors. This plano convex spotlight is available globally except in North
America. The price range of a plano convex is between the Ellipsoidal reflector
and the Fresnal. Plano convex is still a popular and efficient luminaire used
for many lighting applications. Companies like Strand Lighting, ADB and Selecon
are some manufactures which are still manufacturing different models of this
luminaire for countries except North America.
They produce a Plano Convex with a 10 to 65 variable, wattage 300 to 2000 ,
with a round, hard edge beam. As a kit it includes a power cord with an option
of additional pipe clamp, lamp, color frame, electrical connector and a safety
cable.
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