95:. It has a 'stepped' appearance instead of the 'full' or 'smooth' face of other lenses. This allows the lens to focus the light by tilting each successive ring of glass slightly more steeply as its distance increases from the center. If the glass were completely flat, this would cause a corresponding pattern of circles of light, so Fresnel lenses are usually stippled on the flat side. This pattern of small bumps helps to break up the light passing through the lens and gives Fresnels their characteristic soft beam. This means that the intensity of the light is consistent across the spread of the beam of light, as opposed to being less intense around the edges as in an
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at its focus point. This effectively doubles the light delivered by the fixture, as all that is emitted backwards into the reflector is reflected back out the front. As with most lighting fixtures, the lamp and reflector cannot move independently, and are moved together as a unit to focus the beam.
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While the focus can alter the size of the beam, the distinctive scatter of light that the
Fresnel lens emits also requires a way of controlling its shape. Since Fresnels cannot use internal shutters, such as those found in an ellipsoidal spotlight, they are often fitted with distinctive
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Because the reflector of a
Fresnel lantern cannot be larger than its lens aperture, the lamps are not very efficient: only the light emitted straight forward or backward (and redirected forward by the reflector) is utilized, with the rest absorbed by the casing as
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is limited by the length of the housing. To reduce the width of the beam, the lamp and reflector are moved further back from the lens (spot focus). However, the farther back in the housing the lamp is placed, the more light is wasted in the housing.
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In the theater and dance world, Fresnels are most often used for top or backlighting, at medium throw distances. In small venues, they are occasionally used for front light, although the relative lack of control, when compared to an
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This is done by a slider on the bottom of the lantern, or a worm track and crank in the back of the unit. The lamps work best with their bases facing up, with bulb life shortened significantly when mounted upside down.
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to control the spill and shape the beam of light. These are large metal flaps that may be mounted just beyond the color slot at the front of the lantern. They are colloquially known as "Harris Flaps" in the
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Theatrical
Fresnel lanterns are typically made in three-, six-, or eight-inch lens diameters, with lamps ranging in power from 150 W to 2,000 W. The three-inch variety is referred to as an
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In film lighting lenses range in size from 2 to 24 inches, and lamp power between 150 W and 24,000 W.
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Fresnel lanterns in use at a classical concert; they can be seen silhouetted against the stage and each sports a
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The stepped lens design also causes less heat buildup than does a plano-convex lens of the same angle.
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Set
Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution
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A Fresnel with the lens open to show the ridges. There is no lamp in the instrument
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1: Cross section of a
Fresnel lens 2: Cross section of a conventional
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used in a
Fresnel lantern is named after its inventor,
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228:. Unsourced material may be challenged and removed.
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288:Learn how and when to remove this message
362:"Lighting for Cinema, Lighting Controls"
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369:Dr. Shyama Prasad Mukherjee University
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681:Parabolic aluminized reflector light
226:adding citations to reliable sources
144:The degree to which the lamp may be
47:to wash light over an area of the
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666:Ellipsoidal reflector spotlight
311:"How does a Fresnel Lens work?"
213:needs additional citations for
97:ellipsoidal reflector spotlight
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360:Chand, Tushar (1 May 2021).
16:Lantern using a Fresnel lens
59:, and is commonly used for
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816:Stage lighting instruments
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120:Fresnels use a spherical
643:Theatrical smoke and fog
618:Lighting control console
339:. Boston: Focal Press.
177:in certain situations.
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331:Box, Harry C (1993).
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89:Augustin-Jean Fresnel
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676:Intelligent lighting
222:improve this article
633:Stage pin connector
567:Lighting technician
487:Technical direction
190:theatre industry.
79:of equivalent power
33:frəˈnɛl or fruh-nel
572:Master electrician
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781:Video design
766:Sound design
761:Running crew
749:Other fields
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372:. Retrieved
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315:. Retrieved
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278:January 2010
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220:Please help
215:verification
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106:Construction
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45:Fresnel lens
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31:(pronounced
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740:Prompt book
701:Accessories
653:Instruments
433:scenography
171:ellipsoidal
124:, with the
93:lighthouses
67:Description
717:management
691:Striplight
588:Barn doors
518:Fly system
450:Theatrical
442:Scene shop
429:Stagecraft
317:2006-12-12
248:newspapers
194:References
183:barn doors
139:waste heat
61:back light
696:Spotlight
608:Cyclorama
598:Color gel
523:Platforms
163:barn door
122:reflector
57:key light
53:spotlight
810:Category
725:Blocking
581:Hardware
508:Curtains
496:Hardware
126:filament
99:(ERS).
39:used in
797:Outline
638:Top hat
593:C-clamp
533:Weights
482:Rigging
452:scenery
262:scholar
175:special
146:focused
128:of the
41:theatre
37:lantern
555:Fields
503:Batten
460:Fields
374:1 June
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715:Stage
686:Scoop
628:Snoot
513:Flats
365:(PDF)
269:JSTOR
255:books
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771:Prop
613:Gobo
431:and
376:2022
341:ISBN
241:news
130:lamp
85:lens
730:Cue
224:by
153:Use
55:or
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367:.
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27:A
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407:v
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