The Dungog Cinema shows films on industry-standard 35mm
film. The movie arrives at the cinema on spools of approximately 20 minutes, or
2000ft of film. A typical movie fits on 6 spools, and uses up to 12000ft of film
or more! Each frame of film is 35mm and there are 24 frames per second of film. The movie is then 'made-up'
onto 6000ft, or 1 hour, reels, (a 6000ft reel is visible as the large black
round wheel on the top of projector one in the picture below), whereby the
ending of spool one is spliced (joined) to the beginning of spool two, and then
spool two to spool three. The second half of the movie (spools 4-6) are then
made-up onto another reel. Both reels are then loaded and threaded onto the two
projectors (see below).
Then, half-way through the movie, a 'change-over' is performed, where at a
specific point in the movie, the second projector is started up and the picture
continues on the second machine. When performed well, (when Ken does it), the
change-over is seamless and it takes a trained eye watching the movie to pick
where it is.
Trailers are normally assembled on a separate 2000ft reel (see rewind bench
picture at the bottom of the page) and played first, then there is a change-over
to the main feature, however sometimes the trailers are attached on the front of
the main feature's first 6000ft reel.
Pre-movie slides are printed on 70mm transparencies and shown on the slide
projector (fourth picture). The slides are loaded and changed by hand for each
session.
The light source for both the movie projectors and the slide projector is
provided by a carbon arc. This is similar to a welding arc, where high current
is passed through two carbon rods (one positive, one negative) over a small gap
(approx 5 to 10 mm). This creates an extremely intense light, which is focused
by a large mirror and directed through the film running through the projector,
through the lenses and onto the screen. Such an intense light is required
because of how much the image is blown up, from a single 35mm frame of film to
the huge picture you see on the screen.
The sound for film is in two distinct formats, analogue and digital. Digital
sound comes in three different formats; DTS, Dolby Digital and SDDS. Dungog
Cinema uses both analogue and DTS Digital sound.
Analogue sound uses a graphical representation of the sound printed onto the
side of the film. A light shines through the soundtrack as it runs through the
projector, and a photocell (light sensor) picks up the light after it has past
through the soundtrack. The voltage that the photocell creates when the light
falls on it is then processed in the sound processor (black box, 2nd unit down
in the sound rack, see second photo), passed onto the amplifiers and then
outputted from the speakers in the cinema.
On the other hand, DTS digital sound is contained on two separate mediums. A
time code is printed on the film and the actual digital sound is contained on
specialised CDs. A time code reader is installed on both projectors, and
these connect to the DTS unit in the sound rack. (white box in the sound rack
with the CD drives visible on the right hand side, second picture). The DTS unit
receives the time code from the readers, and determines exactly what part of the
film is being shown on the screen and plays the corresponding sound, resulting
in perfect synchronisation between the picture and the sound.
DTS digital sound is far better in quality and dynamics than analogue, however
some movies are not released with DTS sound and so they must be played in
analogue.
When the movie has finished showing at the cinema, it is 'broken down' back onto
the 20 minute spools it arrived on and sent back to the distributors.
All this seems like a lot of information to take in, so
if you have any queries about how the projection and sound systems work, don't
hesitate to email cinema@dungog.org or
ask the staff next time you are at the Dungog Cinema for a guided tour of the
projection booth!
Here are some photos of the projection booth. More to come
soon!!
The booth, showing the two main projectors. Projector one is
closest to camera, (on the left)
The
sound rack, containing sound processor, digital sound unit, and amplifiers
Close
up of projector 2 in action, projecting the first reel of The Pianist
The
slide projector
The
rewind bench, with 2000ft (20 minute) reels
Dungog Cinema is proud to feature
Digital Sound
We Use and Recommend
Amplifiers
