5.1.1 Projector/Lamphouse (Motion Picture Presentation - theatrical projection)
Description
This article is from the rec.arts.movies.tech FAQ, by Scott E. Norwood snorwood@nyx.nyx.net with numerous contributions by others.
5.1.1 Projector/Lamphouse (Motion Picture Presentation - theatrical projection)
The projector is the most critical part of any theater's projection
setup. Many newly installed theaters in the US use new or rebuilt
Simplex or Century 35mm projectors. The most common Simplex models are
the Simplex XL (a.k.a. Pro 35, a currently manufactured model), the
older Simplex E-7, and the really old Super Simplex. The most common
Century models are the SA, the older C, and the 35/70mm JJ.
Larger theaters built from the 1960's through the 1980's may instead
be using combination 35/70mm projectors, like the Norelco AA-II (known
in Europe as the Philips DP-70), and Century JJ, although, with the
decreased availability of 70mm features of late, most of these
machines are either used exclusively for 35mm shows or are sitting
idle.
Most modern theaters use xenon bulb lamphouses of between 2 and 4
kilowatts. This provides a picture of adequate brightness on the
medium-sized screen common in multi-screen cinemas. A larger lamphouse
of up to 5-7 kilowatts is needed for a very large screen, such as that
of a drive-in theater; larger lamphouses offer little increased
benefit for 35mm. Older theaters often still use carbon-arc lamps,
which require more attention on the part of the projectionist than
xenon, but some feel that they offer a light of better color
temperature (i.e. not as cold-looking) than xenon. The general rule of
thumb for xenon lamphouse size is roughly 1kw of power for every ten
feet of screen width; thus a 30-foot screen should require about a 3kw
lamphouse.
As for the film handling system itself, automated cinemas usually use
film `platters,' in which the entire print is loaded onto a large
plate-like device (with the film from the individual shipping reels
spliced together into one continuous roll), permitting one
projectionist to operate the projection equipment for many auditoria.
Smaller theaters and older theaters often use two projectors with
small reels, each holding either 2000' each (just like the shipping
reels) or 4000-6000' each (with the contents of two or three shipping
reels spliced together). Between the reels, the projectionist operates
a changeover mechanism, simultaneously switching over machines and
soundtracks. He then rewinds the next reel, reloads it on the idle
projector and prepares for the next changeover.
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