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==Projectors== [[File:Xenon IMAX 1.jpg|thumb|The 15 kW [[Xenon arc lamp|Xenon short-arc lamp]] used in IMAX film projectors, as seen here, being displayed at the [[Montreal Science Centre]]]] Transporting the large film stock through the optical system presented challenges for both the camera and the projector. Conventional [[70 mm film|70 mm]] systems were not steady enough for the 586Γ magnification. On the projector side, William Shaw adapted an Australian patent (no. 291,375) for film transport called the "rolling loop" by adding a [[compressed air]] "puffer" to accelerate the film, and put a [[cylindrical lens]] in the projector's "aperture block".<ref>{{cite web|url=https://www.in70mm.com/newsletter/1997/48/imax_projector/index.htm|title=The Basics of The Rolling Loop IMAX Projector|website=In70mm.com}}</ref> The rolling loop mechanism is used to move the film in projectors and cameras; the sprockets in the film are only used for registration as the film is too large to be moved with sprockets at the necessary speeds for projection and filming without damage. The projector uses a [[vacuum]] to pull the film into contact with this lens. Thus the "[[Field flattener lens|field flattener]]" flattens the image field. The lens is twice the height of the film and connects to a [[pneumatic]] [[piston]] so it can be moved up or down while the projector is running. This way, if a piece of dust comes off the film and sticks to the lens, the projectionist can switch to a clean portion of the lens at the push of a button. The lens also has "wiper bars" made of a [[felt]] or brush-like material that wipes dust off the lens as it moves up or down.<ref>{{cite web |title=AU 6:50 / 15:59 70mm IMAX Projector Lacing: Science Museum, London |url=https://www.youtube.com/watch?v=BG-ZB-FY88E&t=410s |website=Youtube | date=June 10, 2023 |publisher=bored_tech |access-date=22 August 2023}}</ref> The projector uses a vacuum to keep the film flat and oriented correctly for projection.<ref name="auto"/> The shutter of an IMAX projector is also kept open for longer than a 35 mm projector shutter to increase image brightness.<ref name="auto2"/> IMAX projectors are [[pin]]-stabilized; this means that four registration pins engage the [[perforation]]s at the corners of the projected frame to ensure perfect alignment. Shaw added [[Cam (mechanism)|cam]]-controlled arms to decelerate each frame to eliminate the microscopic shaking as the frame "settled" onto the registration pins. The projector's [[Movie projector shutter|shutter]] is open around 20% longer than in conventional equipment, and the light source is brighter. The [[Xenon arc lamp|xenon short-arc lamps]] are made with a thin envelope of [[fused quartz]] and contain [[xenon]] gas at a pressure of about 25 [[atmosphere (pressure)|atmospheres]] ({{convert|367|psi|abbr=on|sp=us}}). Because of this, projectionists are required to wear protective [[Bulletproof vest|body armor]] when changing or handling the lamp in case it breaks (e.g., due to a drop to the floor) because of the danger from flying quartz shards propelled by the high pressure of the xenon gas within; this applies to all projection xenon lamps. An IMAX xenon lamp runs on DC power, lasts for 1,000 hours and requires its own pump and water cooler. The projector's optics also require compressed air cooling.<ref name="auto1"/> An IMAX projector weighs up to 1.8 tonnes (2 [[short tons]])<ref name="auto2"/> and is over {{convert|178|cm|ft|1|abbr=on}} tall and {{convert|195|cm|ft|1|abbr=on}} long.{{citation needed|date=June 2020}} The projector is raised and locked into position before each screening.<ref name="auto1"/> IMAX Corporation has released four projector types that use its 15-perforation, [[70 mm film]] format: '''GT''' (Grand Theatre), '''GT 3D''' (dual rotor), '''SR''' (Small Rotor), and '''MPX''', which was designed for retrofitted theatres.<ref>{{cite web|url=http://www.imax.com/images/corporate/pdfs/filmmaker.pdf|title=The 15/70 Filmmaker's Manual|access-date=December 29, 2009|publisher=Imax|url-status=dead|archive-url=https://web.archive.org/web/20091229035233/http://www.imax.com/images/corporate/pdfs/filmmaker.pdf|archive-date=December 29, 2009|df=mdy-all}}</ref> In July 2008, the company introduced a digital projection system, which it has not given a distinct name or brand, designed for multiplex theatres with screens no wider than {{convert|21.3|m|ft|abbr=on}}. All IMAX projectors, except the standard GT system, can project [[Stereoscopy|3D images]].<ref>{{cite web |last=Chang |first=Michael |date=2022-01-09 |title=Buyer's Guide For 3D Projector |url=https://www.projectorchannel.com/buyers-guide-for-3d-projector/ |access-date=2022-02-28 |website=Projector Channel |language=en-US}}</ref><ref>{{cite web|date=2012-02-09|title=IMAX β The Giant Step to Movies, WOrking, Technology, Comparison|url=https://www.circuitstoday.com/imax-β-the-giant-step-to-movies|access-date=2020-11-19|website=Electronic Circuits and Diagrams-Electronic Projects and Design|language=en-US}}</ref> GT 3D projectors require two separate lamps and polarized projection optics.<ref name="auto"/>
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