35mm Glossary

The following is a fun and unofficial overview of some commonly used 35mm projection terms. For use in understanding terms used in casual conversation -- any attempts to use this as a training guide are at your own risk!

2000s/6000s

Sometimes called reels, sometimes called spools (and a specific variety of 6000 is sometimes called a bicycle wheel), these are what the film gets wound onto. Named after the number of feet of film they hold, a 2000 holds one reel and a 6000 holds three.

Anamorphic

An additional lens used for scope, which stretches the film out widthwise.

Aperture plate

A metal plate which ‘crops’ the film to the required aspect ratio.

Archive print

A particularly special print from (particularly the BFI) archives, only allowed to be played by a very limited number of cinemas. Prints from the BFI archives can only be played via single-reel changeover. Treat with care!

Breaking down

Separating spliced-together reels of film after playing, to be packed away and sent back to distributors.

Changeover

The process of swapping from one projector to the other mid-film at the end of a reel. Achieved with careful attention to cue dots and very precise timing!

Changeover shutters

Quick-moving shutters in front of the lamp in each projector. During a changeover, one opens exactly as the other closes, giving a seamless change.

Chinagraph

Funky pencil which can draw on smooth surfaces like film. Often used to mark splices between reels of film.

Cue dots

Two sets of markings (usually black blobs or white rings) at the end of each reel, to tell the projectionist when to change over. They serve two purposes – the first (motor cues) tell the projectionist to start the second projector, and the second (changeover cues) tell the projectionist when to swap projectors. Never call them cigarette burns!

Down

To down the projectors means to close the changeover shutters and dowsers, so no image is projected on screen.

Dowser

A hefty sheet of metal which blocks the lamp, to stop the lamp melting everything in its path.

Edge damage

Damage to the edges of the film – self explanatory! Unrepaired damage can result in films snapping or dodgy sound.

FilmGuard

Magical (and expensive) cleaning and lubricating liquid for film. Cleans off dirt and fills in scratches.

Film stock

The material the film is printed on. Was originally nitrate (highly flammable, and now carries such strict safety regulations that very few places can play it), but due to the spontaneous combustion we moved to acetate (which can break down over time and snap easily), and nowadays new films are printed on polyester (more durable and less snappable!). Celluloid is sometimes used as a catch-all term, but really this specifically means nitrate.

Footer

Has two meanings! Either refers to the few feet of (mostly black) film after the picture ends, or refers to the 18-ish frames after the changeover cues.

Gate

Refers to the part of the projector which holds the film steady in front of the lamp. We say a frame is ‘in the gate’ if it’s in the projection aperture.

Gate burn

When the film stops moving and the frame that’s in the gate is exposed to the heat of the lamp for more than a fraction of a second, and melts.

Gate tension

How tightly the gate is holding the film. Too loose and it’ll wobble, too tight and the projector will strain to pull the film through.

Header

A few dozen feet of film at the start of each reel, before the picture starts. Has numbers marking each foot, to allow the projectionist to lace each reel at the right position.

Intermittent

A mechanism in the projector, which pulls down one frame of film at a time, moving every 1/24th of a second. Means each frame is held still in front of the lamp to give a steady picture. Also used as shorthand for the sprocket turned by this mechanism.

IPA

An alcohol solvent used to clean tape residue and other miscellaneous dirt off film.

Lamp

The very bright, very hot xenon lamp in each projector. The light emanates from an arc of xenon plasma, the tip of which reaches temperatures up to the surface of the sun! ‘Striking the lamp’ means to turn it on.

Lamphouse

The metal box housing the lamp.

Lacing

Putting the film into the projector. Also known as threading (by the Americans).

Lens

You know what a lens is! Requires a different one for each aspect ratio.

Liv

The poggest pogjectionist. Do not call this Olivia.

Loops

The top loop and bottom loop are two set amounts of slack left when lacing, to avoid shredding the film when the intermittent moves.

Make up table (MUT)

Used for winding film onto and off of the decks of a platter.

Making up

Winding through each reel of film to check splices, look for damage, and record information about the print.

Penthouse

An auxiliary sound reader at the top of the projector – on ours, these are the SDDS, DTS and magnetic sound readers.

Perforation

The holes on both sides of the film, which fit onto the teeth on the sprockets in the projector. Each frame has four perforations. Also known as sprocket holes.

Picture stability

How stable the picture is on screen! The worse the picture stability, the more the film wobbles on screen – vertical wobbles are called jump/bounce, and horizontal wobbles are called weave.

Platter

A contraption composed of a number of massive stacked discs. Projectionists can splice an entire film together and wind it onto the platter to play the whole thing through one projector – after it’s finished playing it’s immediately ready to play again. Sometimes called a cake stand!

Racking

Positioning the film in the gate so the right part of each frame is projected on screen. If this is wrong, we say the film is out of rack.

Rectifier

Converts high-voltage mains AC and converts to low-voltage (very high current) DC for the projectors. (Different from the usual electronics meaning!).

Reel

A reel is a length of about 2000 feet of film (about 20 minutes) with cue dots on the end. Films are separated into reels for transport and storage. Also sometimes refers to the 2000s and 6000s which film is wound onto.

Scratch

Can be either an emulsion scratch (on the emulsion side where the picture is printed), which appears colourful on screen, or a base scratch (on the base of the film stock), which appears black on screen.

Sound formats

There are many flavours of film sound: Mono, A-type, SR, SRD/Dolby Digital, DTS, SDDS. One print may have multiple available formats. Each has its own benefits and drawbacks!

Sound processors

We’ve got four sound processors for 35mm: The XD10 (for DTS), an SDDS processor (you’ll never guess) and the CP650, or its decrepit ancestor the CP500 (for everything else).

Sound trailer

A short trailer attached to the start of each film, to showcase the capabilities of the sound format being used. Each sound trailer is for a specific sound format, so it’s important to choose the right one for each film.

Splice

A join between two pieces of film, or the act of creating such a join.

Sprocket

A rotating wheel in the projector, with teeth on it which fit into the perforations on the film, in order to move the film through the projector.

Tilt

The angle of the projector. May need to be adjusted to ensure the film is projected centrally on the screen.

Tower

Another method of playing an entire film off one projector. Two very large reels (12000 feet or more!) turned and controlled by the tower’s own motor. Once played through, the film needs rewinding before playing again.

Variable Area/Density

Optical soundtracks come in two flavours, variable area (printed as a white area of varying width on a black background) and variable density (printed as a grey strip of varying shades).

Winding bench

Either electric or manual, a contraption which allows the projectionist to wind through a film to make it up or break it down.

Originally by Liv Lancastle with fact-checking by Kieran Hall and the projection team, 2023!