Reflectors

  • Spherical
  • Parabolic
  • Elliptical

Lenses

  • Concave
  • Convex
  • Plano Convex
  • Double Convex
  • Fresnel

Fixtures

 

Dimmers

Protocol

Consoles

 

Reflectors

The Reflector: The reflector fulfills two purposes:

1.      To increase the efficiency of the instrument by deflecting light that would otherwise be unused.

2.      To create specific patterns and qualities by the redirection of light. 

The law of specular reflection explains what happens to light when it strikes a smooth, shiny surface, such as a mirror.  Light will be reflected at an angle equal to the angle which it struck, but in the opposite direction.  Early stage equipment used moulded glass as reflectors, but they have been replaced by lightweight spun-metal reflectors that are coated with a highly reflective and durable surface. Stage lighting instruments use one or possibly a combination of three reflector types: spherical, parabolic, and ellipsoidal.

Parabolic Reflector:
If a light source is placed in the focal point of a parabolic reflector, the rays of light will be reflected parallel to one another.  This will give a great concentration of light in a tight beam, rather than an effused spread. Moving the source toward the reflector will spread the light, while moving the source away from the reflector will cause the light rays to converge.  This type of reflector can be found in some floodlights, beam projectors, scoops and PAR lamps.

Spherical Reflector:
If a light source is placed in the center of a spherical reflector, all of the rays will be reflected back 180 degrees of their original trajectory.  This gives almost double the light output than would occur without the reflector.  A spherical reflector in concert with a special Fresnel lens is used for Fresnel spotlights. This type of reflector is commonly used in Fresnels and Beam projectors. A spherical reflector will increase the efficiency of a lighting instrument by 40%.

Ellipsoidal Reflectors:
The ellipsoidal reflector is more efficient than either the spherical or parabolic.  By mathematical definition an Ellipsoid has two focal points.  When a reflector is placed at the focal point at that end, all rays of the light that strike the reflector will be diverted through the second focal point.  The result is that an enormous percentage of the light from the source is directed in a manner that makes it easily usable. Ellipsoidal reflectors are used in Ellipsoidal instruments and can improve the efficiency of an instrument by 75%.

 

The Housing:The housing controls the excess light that has not been reflected in the desired direction. It is generally painted black both internally and externally to contain stray light and to keep the instrument from attracting attention to itself. The housing also includes the color holder slot, or gel holder slot.

Dichorism:
Dichoric filtration  refers to the ability of material to pass certain wavelengths of light through its surface while rejecting others.  This principle has been applied to color filters, and is also now also used in reflectors.  By reflecting the light wavelengths which are visible, while allowing the heat wavelengths to pass, the light being reflected is cooler and less likely to burn through gels, or heat the front end of a light to the point that it will burn you when you are focusing the instrument.

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Lenses

Fresnel Lens

Multifocal Fresnel lens


Concave

 

Convex

 

Plano Convex

 

Double Convex

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Fixtures
 

Fresnel
Fresnel Lens 
The Fresnel lens was invented by French physicist Augustin Fresnel in 1827, who used prisms to capture and concentrate 90 percent of a lamp’s light and focalizing it into an intense horizontal beam. The precise manufacturing needed produce the lens—hand-ground from perfectly molded lead crystal—required the skill of an artisan. His invention improved lighthouses’ range from a few miles to almost 20.


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Parnel

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Ellipsoidal

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Par Can

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S4 Par Can

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Beam Projector

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Far Cyc

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Follow Spot

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Linenbach

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Scene Machines

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Pani

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Wiggle Lights

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Resistance  Dimmers

 

This is an older obsolete type of dimmer where excess power is bled off into heat. The biggest disadvantage to this type of dimmer is that there is always a load on the dimmer--as soon as the dimmer is turned on the dimmer will use 100% of its power. If the circuit attached to the dimmer is set to 20% then 80% of the power is bled off into heat coils. If the circuit is set to 0% then 100% of the power is bled off into heat. Another problem with resistance dimming is that in addition to having a maximum load (the maximum amount of power which a dimmer can safely take) a resistance dimmer also has a minimum load. In order to get effective dimming these dimmers must have at least their minimum load. Often in order to make these minimum loads resistance dimmers were loaded with "Ghost Loads" or extra electrical equipment offstage in order to make these minimum loads. This is a huge disadvantage because of how wasteful the system was as well as how difficult it was to control.

 




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Auto Transformer



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Triacs



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SCR



A diac is a form of solid-state switch used to switch AC voltage; it belongs to the class of switches known as thyristers. It is like a junction transistor without a base lead (it is a two-lead device) and accomplishes its switching action by breakdown at a certain voltage. There are also four layer devices with a similar mode of operation known as four-layer diodes.



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SSR


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Protocol
Analogue

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AMX-192

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MicroPlex

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DMX-512

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Proprietary

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Consoles

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Manual

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Memory Assisted

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Computer

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Moving Light

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