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Ch. 4 Lenses, Lamps, Reflectors, & Lighting Instruments - Coggle…

- - - - The Pyrex glass or synthetic quartz container for a lamp filament and gaseous environment.
    - - The light-producing element of a lamp; usually made of tungsten wire.
  - - - An electric current that leaps the gap between two closely placed electrodes.
    - - Light source in which two electrodes operate in the open air.
  - - - One millionth of a watt.
    - - They produce colored light of a specific wavelength without the use of external filters.
      - The shape of the LED case can be designed to focus light to a specific beam width.
      - They have an expected life of 100,000 hours.
      - They dim over time rather than burning out abruptly.
      - They provide more light output per watt.
      - Their operational temperature is cooler than almost any type of lamp.
    - - PAR
        
        Acronym for parabolic aluminized reflector. A sealed-beam lamp with a parabolic-shaped reflector covered by a thin, reflective aluminum coating.
  - - - The bulb is the Pyrex or synthetic quartz envelope that encases the filament and acts as a container for the gas-filled atmosphere of the
    - - The lamp base secures the lamp in the socket and provides the electrical contact points between the socket and the filament.
    - - Various lamp filaments are available, each designed to perform a particular function.
  - - - A device for measuring specific wavelengths of light.
    - - A measurement from 0–100 that determines the range of colors that a source or instrument make visible. 100 indicates full range.
  - - - An international unit of illumination. One footcandle equals one lumen of light falling on a surface area of one square foot. 6
    - - Specification sheets. Data sheets providing information about equipment such as lighting instruments, dimmers, and so forth.
    - - How far light from an instrument travels from its hanging position to the center of its area of focus.
    - - The distance from the projector to the screen.
  - - - The spherical reflector, Figure 4.15A , is shaped like a section of a sphere with the center of the lamp filament placed at the center point of the sphere (F1).
    - - A theoretical concept: All light emanates from a single point that has no dimensions. In the real world all light sources, such as filaments, have height, width, and depth.
    - - In this case, refers to a comparison of the intensity of light emitted by the lamp with the intensity of light emitted by the instrument.
    - - An instrument with a relatively hard-edged light quality. So called because it has a planoconvex lens.
    - - Reflectors An ellipsoidal reflector is officially known as a truncated conical ellipse.
    - - Figure 4.17 illustrates that if a lamp filament is placed at the focal point (F1) of a parabolic reflector, the light bouncing off that reflector will be directed forward in a relatively coherent beam of light.
    - - ,car headlights, and aircraft landing lights all have parabolic reflectors. In all of these applications the parabolic shape of the reflector creates a fairly cohesive beam of light, while the dispersion characteristics—narrow/medium/wide beam spread—and beam shape—round/oval—are controlled by the lensatic properties of the front lens, which also functions as the front cover for the lamp.
    - - Combination reflectors, as you probably figured out, combine the characteristics of more than one type of reflector shape.
    - - There are two primary types of materials used to make reflectors: metal and glass.
    - - A filter that reflects, rather than absorbs, unwanted wavelengths of light while allowing the desired wavelengths to pass through the filter.
- - - - A lens with one flat and one outward-curving face.
    - - (1) (Lighting fixtures) One or more lenses, placed at a specific distance from the source (and from each other when two or more lenses are used) to create the desired angle of dispersion of the light.
      - (2) (Film/video) The path taken by light as it passes through the lens into the camera and onto the film or electronic receptor.
    - - The distance from the lens at which the light rays converge into a point; for lenses used in stage lighting instruments, the focal length is most frequently measured in whole inches.
    - - Two plano-convex lenses placed with their curved surfaces facing each other; creates a system that has a shorter focal length than either of its component lenses.
  - - - A type of step lens with the glass cut away from the convex face of the lens.
    - - To soften the appearance of light by using a translucent filtering element to scatter the rays.
- - - - A lighting instrument characterized by hard-edged light with little diffusion; designed for relatively long throws, it is manufactured with fixed- and variable-focal-length lenses; the light beam is shaped with internally mounted shutters.
    - - In this instance, any light that is visible outside the clearly defined edge of the fixture’s projected beam.
    - - The ERS operates on the basic principle of using an ellipsoidal reflector to gather light from one focal point and focus it on the second focal point, as described earlier in this chapter. The shutters, made of stainless steel or some other highly heat resistant metal and used to shape the edges of the beam, are located in a plane close to the second focal point.
    - - An ellipsoidal reflector spotlight with movable lenses that allow the focal length to be changed. The lens or lens train is placed in front of the shutters to focus the light into the desired field angle, as illustrated in Figure 4.20 .
    - - That point where the light emitted by an instrument is diminished by 50 percent when compared with the output of the center of the beam.
    - - That point within a lighting fixture’s cone of light where the light diminishes to 10 percent of the output of the center of the beam.
    - - Although the specific lamp that is used with any instrument depends on the design of the instrument, some fairly standard wattages are used with various families of instruments.
    - - Refers to a beam of light, the output of which is essentially smooth from edge to edge when measured perpendicular to the axis of the beam.
    - - Refers to a beam of light, the output of which has a noticeable hot spot in its center when measured perpendicular to the axis of the beam. Peak field reading taken at the center of the hotspot.
    - - The straight-line edge created when an ERS’s shutter is inserted into its beam of light.
    - - A lightweight metal holder for color media that fits in a holder at the front of a lighting instrument.
    - - A thin metal template inserted into an ellipsoidal reflector spotlight to project a shadow pattern of light.
    - - The most basic accessory for use with an ERS is the color frame ( Figure 4.24 ), a lightweight-metal holder for plastic colored media. The color frame is inserted into the holder on the front of the ERS.
    - - A hand-held router similar to a dentist’s drill, which can be equipped with a number of bits for grinding, cutting, or carving of wood, plastic, and metal.
    - - A device with movable overlapping metal plates, used with an ellipsoidal reflector spotlight to change the size of the circular pattern of light.
    - - The opening in a lens that allows light to pass through to the film or electronic collector plate. A variable aperture allows the size of the opening to be changed.
    - - A spotlight that produces a soft, diffused light; the fresnel lens is treated on the plano side to diffuse the light.
  - - - Principles The fresnel spotlight is a very basic fixture. The instrument housing holds the lens and provides a mounting platform for the socket, lamp, and small spherical reflector assembly, which are mounted on a small sled that moves closer to or farther from the lens during focusing.
    - - An accessory for a fresnel spotlight whose movable flippers are swung into the beam to control it.
    - - An accessory for a lighting instrument that masks the beam to create a smaller circular pattern of light. Also used to prevent flare or spill.
    - - A long narrow trough-like instrument with three or four circuits controlling the individual lamps; each circuit is normally equipped with a separate color; used for blending and creating color washes; also known as an X-ray. Can also be written as “strip light.”
  - - - A long narrow trough-like instrument with three or four circuits controlling the individual lamps; each circuit is normally equipped with a separate color; used for blending and creating color washes; also known as an X-ray. Can also be written as “strip light.”
    - - A large expanse of cloth or drop used to surround the stage. Also called a cyc.
    - - A glass color medium for use with striplights; frequently has diffusing properties.
    - - A lensless instrument with an asymmetric reflector used to create a smooth wash of light on a cyclorama or sky tab from a relatively close distance.
    - - Cyclorama. A large drop used to surround the stage.
  - - - A lensless instrument with a conical ellipse reflector; used for lighting cycloramas and drops; also known as a scoop.
  - - - A holder for a parabolic aluminized reflector (PAR) lamp; creates a powerful punch of light with a relatively soft edge; the PAR 64 is commonly used for concert lighting.
  - - - (1) Thin pieces of metal used to shape an ERS’s beam of light, typically used in sets of four.
        (2) lever-actuated device, also called a chopper, used to control the height of the top and bottom edges of a followspot beam.
- - - - A device that changes the voltage in an electrical system; the output voltage of a step-down transformer is less than its source; a step-up transformer increases it.
    - - A transformer whose output voltage is lower than its input voltage.
    - - A term used to describe a lighting fixture that is “standing up” on a pipe. The yoke of the fixture is attached so it places the fixture above the pipe. Also referred to as “yoked up,” and/or “roostered.”
    - - Hung beneath. Lighting instruments are typically suspended underneath a pipe. A clamp is attached to the pipe and the body of the fixture hangs from a yoke suspended below the clamp.
    - - A vertical pipe with horizontal crossbars hung from the end of an onstage electric pipe or dead-hung from the grid. Used as a hanging position for lighting equipment.
  - - - See overhung .
    - - A pipe, hung in the wings, running downstage to upstage; often used for hanging masking and/or lighting equipment.
    - - Typically, anything suspended directly from the grid without any mechanical means of raising or lowering it.
    - - The metal beams above the stage (at the top of the flyhouse in a proscenium theatre) to which the rigging system is attached. The metal beams are typically laid out in a gridiron pattern, hence the name.
    - - A catwalk, typically in the wings and above the stage floor. Named for the wooden or metal belaying pins used to tie off objects flown with (typically) a rope and sandbag system.
    - - Extremely strong, flexible, multistrand, twisted metal cable; 1/8-inch aircraft cable has a breaking strength of one ton.