Lenses Double Plano-Convex Lens Train

Lighting designers and those involved in technical production need to have a thorough working knowledge of both electricity and electronics

Lenses Double Plano-Convex Lens Train This consists of two plano-convex lenses placed with their convex surfaces toward each other This double configuration provides the same optical properties as a single lens of greater thickness and curvature, and the total thickness of the two lenses is less than the thickness of the optically comparable single lens

Lenses Step Lens A step lens retains the optical characteristics and shape of a plano-convex lens, but the glass on the flat side is cut away in steps The stepping process gives the lens the optical properties of a thick, short-focal-length, plano-convex lens while eliminating its negative characteristics Finishing the edges of the steps with a flat-black ceramic coating eliminates the spectral breakdown

Lenses Fresnel Lens The Fresnel lens is a type of step lens with the glass cut away from the convex face of the lens instead of its plano side The advantages of this lens include reduction of the thickness of the lens, which allows more light transmission and lessens the chance of heat fracture Fresnel lenses are primarily used in Fresnel spotlight

Lamps Incandescent Lamp The standard incandescent lamp contains a tungsten filament that is place in an inert gas environment inside the lamp bulb The average life expectancy of a regular incandescent lamp used in stage lighting is 50-200 hours

Lamps Tungsten-Halogen Lamp The T-H lamp is primarily the same as the standard incandescent lamp except that the atmosphere inside the bulb is a halogen, or chemically active, gas instead of inert gas Many T-H lamps designed for stage lighting are rated from 150-2,000 hours

Lamps Arc Sources An electronic arc that produces brilliantly blue white light is created when an electric current jumps the air gap between two electrodes An arc is used as the source of some followspots Neither arc nor encapsulated arc sources can be dimmed, so they are normally not used in nonautomated stage-lighting instruments

Lamps Color Temperature All the standard light sources appear to be white; however, they are actually a variety of colors These colors can be identified using the color-temperature scale The color-temperature scale is measured in Kelvin (K) The higher the light output of a lamp, the higher its color temperature and shorter its rated life Instruments that are “gelled” are generally equipped with lamps of the same color temperature Gel—to put a color filter into a color frame and place it in the color-frame holder of a lighting instrument

Lamps Lamp Structure All lamps are composed of three basic parts Bulb—the Pyrex or synthetic quartz envelope that encases the filament and acts as a container for the gas-filled atmosphere of the lamp Base—the lamp base secures the lamp in the socket and provides the electrical contact points between the socket and the filament Filament—for stage lighting, the lamps are make of a tungsten-wire, tightly coiled, and strung in one of the general configurations

Lamps MR16 Lamps Small-diameter, low-voltage, low-wattage lamps that integrate a small, coiled-filament tungsten-halogen lamp into a focusing mirrored reflector It is available in a variety of voltages and wattages as well as several beam-angle widths from very narrow to flood

Lamps Light Output of Lamps The light output of an incandescent lamp is primarily a function of the size and composition of the filament This output is measured in lumens

Lamps Light Output of Lamps Color Media Plastic—the majority of filters used in theatrical lighting are made of either Mylar or polyester because of the rugged, long-lasting, heat-resistant qualities of these plastics

Lamps Light Output of Lamps Color Media Glass These filters are used infrequently because they are heavy, expensive, and shatter if dropped They are most often used in roundels, the glass filters used with striplights

Lamps Light Output of Lamps Color Media Dichroic They are a relatively new addition to theatrical color media While plastic and glass filters allow their color to pass through the filter while absorbing the undesired color, dichroic filters reflect the unwanted colors To produce a particular color, you use the filter to remove its complementary

Lighting Instruments Ellipsoidal Reflector Spotlight This light has a narrow beam width and is capable of traveling long distances Known as a Leko, the quality of light produced is hard edged with little diffusion The shape of the light is controlled by internally mounted shutters The spill from an ERS is minimal

Lighting Instruments Ellipsoidal Reflector Spotlight Accessories Color frame — a lightweight metal holder for plastic colored media Gobo—a lightweight metal cutout that turns the ERS into a pattern projector Iris—a device with movable overlapping metal plates used to change the size of the circular pattern of light

Lighting Instruments Fresnel Spotlight This spotlight produces a soft, diffused, luminescent light The standard Fresnel spotlight is equipped with a Fresnel lens producing a circular beam of light Oval-beam Fresnel lenses produce an oval beam of light

Lighting Instruments Fresnel Spotlight Accessories Barn door—movable flippers swung into the beam to control the spotlight Funnel—masks the beam to create a circular pattern, also called a snoot or top hat

Lighting Instruments Striplight This light is used to create a smooth wash of light It resembles a long trough with a series of lamps inside The individual lights within the instrument are wired in parallel to form three or four circuits, allowing for mixing and blending of color Striplights are primarily used to light background drops and cycloramas

Lighting Instruments Cyc Light The cyc light is superior to the striplight for creating a smooth wash of light over the expanse of a cyc or drop The cyc light emits a much smoother light than does the stripight and is equiped with a color-frame holder so the light can be colored as desired

Lighting Instruments Ellipsoidal Reflector Floodlight Also known as the scoop, this light is used to light drops and cycloramas It is a lensless instrument that provides a wide, smooth wash of light

Lighting Instruments PAR Can The parabolic aluminized reflector (PAR) is a sealed-beam lamp similar to the headlight of an automobile The PAR can performs no function other than safely holding the lamp and its color media It is used in dance and concert light and is finding increased usage in the theatre

Lighting Instruments Followspot The followspot is used when a high-intensity, hard-edged beam of light is required to follow a moving performer Portions of the system can be adjusted to focus the light and adjust the crispness of the edge of the beam Some followspots are equipped with a dimming device called a “douser” Followspots are also equipped with a color boomerang to control color Douser—a dimming device that can be used to achieve a slow fade-in or out of the light

Specialty Instruments Low-Voltage Sources A number of specialty lamps use a voltage lower than the 120 output volts of most stage dimmers A number of lighting instruments and projectors have been designed to take advantage of the properties of low-voltage lamps

Specialty Instruments Intelligent or Kinetic Instruments Moving light fixtures provide punch, emphasis, and focus Kinetic fixtures and digital control equipment provide the LD with the capabilities to create the in-your-face lighting that supports the production concepts and mood of many concert productions Kinetic fixture beams pan the stage, zoom in and out, change shape, change color, diffuse and sharpen, gobos materialize, spin around, and change patterns

Specialty Instruments Color Changers Color changing is accomplished with either a color scroller or a dichroic color changer The color scroller is used with an ERS, Fresnel, PAR, ,or any other instrument that doesn’t have internal color changing abilities

Dimmers Dimmer-Control Techniques Mechanical Dimmer Control Older types of dimmers require direct mechanical manipulation of an axle running through the central core of the dimmer to adjust the intensity of a lamp This method of dimmer control is awkward

Dimmers Dimmer-Control Techniques Electronic Dimmer Control When you move a controller to increase or decrease the intensity of lights connected to an electronic dimmer, you are using a low-voltage control circuit to manipulate the high-voltage output of that dimmer Until recently, analog control systems were the only method available, now digital is the standard

Dimmers Dimmer-Control Techniques Autotransformer Dimmer These dimmers increase or decrease lamp intensity by varying the voltage within the circuit This type of dimmer is only rarely used to control stage lights, but houselights in some theatres are controlled this way

Dimmers Dimmer-Control Techniques Silicon-Controlled Rectifier Dimmer The SCR dimmer is the most reliable and efficient unit The SCR dimmer operates on a gating principle, which is a rapid switching on and off of the power These properties result in a dimmer that is rugged, long lived, compact, relatively lightweight, moderate in cost, and reasonably quiet in operation

Dimmers Dimmer-Control Techniques Insulated Gate Bipolar Transistor Dimmer The IGBT dimmer is the latest in the continuing line of dimmer development The IGBT dimmer is lighter and quieter in operation than the SCR It has a relatively slow power ramp which reduces the amount of filament hum of an y lamp being dimmed by it

Dimmers Dimmer-Control Techniques Control Consoles Group Master—individual dimmers are controlled by a submaster, which is subsequently controlled by a grand master Preset—allows you to keep ahead of the onstage action by presetting the intensity levels for each dimmer before it is needed

Dimmers Dimmer-Control Techniques Control Consoles Combination—a fusion of the previous two, each dimmer channel has an associated switch capable of assigning the dimmer to preset, group-master, or independent control Computer Memory—the standard for the industry, the computer electronically stores the levels of all dimmers on each cue

Cables and Connectors Electrical Cable for Stage Use The National Electrical Code (NEC) stipulates that the only electrical cables approved for temporary stage wiring are types S, SO, ST, STO These cables have stranded copper conductors and are insulated with rubber or thermoplastic

Cables and Connectors Wire Gauge The American Wire Gauge (AWG) system rates wire according to the amount of current that a conductor of a particular size and composition can safely carry The NEC stipulates that receptacles used to supply incandescent lamps on stage must be rated at not less than 20 amperes and must be supplied by wires of not less than 12 gauge

Cables and Connectors Connecting Devices Several different styles are used in stage lighting Twist-lock connectors Pin connectors Grounded pin connectors The Edison, or parallel blade, plug The NEC stipulates that each plug should be equipped with an effective cable-clamping device to secure the connector to the jacket of the cable

Cables and Connectors Extension Cables Extension cables can be purchased or made in the electrical shop in any reasonable length A two-fer is used to connect two instruments to the same circuit

Circuiting Permanent Wiring The simplest method is to permanently wire the instruments to the dimmers To operate the system, you just turn on the dimmers Although this method is easiest to operate, it provides little flexibility and does not allow for much creativity

Circuiting Spidering Also known as direct cabling, it involves running a cable from each lighting instrument directly to the dimmer to which it is assigned Used extensively in Broadway theatres and on tour, it provides the greatest flexibility because it allows the designer to put an instrument wherever it is needed

Circuiting Connecting Strips and Patch Panels Two advantages: The light plot can be hung and circuited quite rapidly The system provides a great deal of flexibility by enabling you to patch any circuit into any dimmer

Circuiting Dimmer per Circuit The dimmer-per-circuit configuration combines the efficiency in hanging and circuiting of the connecting strip with the ease of operation of the permanently wired system The onstage end of each circuit terminates in an outlet on a connecting strip The other end is directly wired to a dimmer

Lenses Double Plano-Convex Lens Train