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Section IX: Technical equipment

9.1 Film specific practices and procedures and equipment

 

9.1 Film specific practices and procedures and equipment

Harald Brandes and Eva Orbanz

1 Introduction

If motion pictures are to be preserved for long periods of time, they must be stored, under the best possible conditions. They must be examined and tested regularly and, if necessary, copied or technically restored. Each of these processes - examination, testing, restoration and storage, as well as printing and projecting involves passing the film through machines.

Film as a mass medium is the result of a highly developed technology. As far as possible, audio-visual archives employ the technologies used by the respective mass media. However, examination and restoration in particular, require certain specialized items of equipment.

There is a steady development in film techniques, as well as in technical equipment for handling films. A film archive that was equipped with the most up-to-date equipment when it was founded will, in time, find itself with obsolete equipment unless it has organized a refurbishment programme to replace the original machinery with more modern, improved models as necessary. It is essential, therefore, not only to have funds to purchase and install equipment, but also to have it properly serviced, repaired and replaced when obsolete. Film archive equipment is sophisticated and expensive and should be treated accordingly.

For financial reasons, and because personnel training and technical expertise should advance together with the increasing complexity of equipment, it is strongly recommended that the archive operates on a step-by-step basis. By this means, the range and complexity of equipment is gradually increased.

Any piece of equipment is only as effective as the person operating it. It is essential for technical staff to be given adequate training either in their own country or, if necessary, abroad. This may be done most effectively by arranging for in-service training at film laboratories. At present, many laboratories are willing to co-operate once the tasks and duties of an archive are explained to them and it becomes clear that the archive is not a competitor but a potential customer for their services. The need for this training cannot be over-emphasized; the experience gained by this method can, moreover, be transmitted to others within the archive.

Because it is recommended that the archive should not start with sophisticated, expensive equipment, this does not mean that "less sophisticated and inexpensive" should be equated with "poorer quality". Nor is it necessary to purchase only new equipment. Used equipment may well prove to be exactly what is required in quality and, in addition, will be considerably less expensive.

The size of the archive's collection of films, its policy on preservation and conservation and in giving public access are directly related to the importance and size of the technical department, the size and level of training of its staff and the type of equipment used. A logical and necessary consequence of relating the size and the use of a collection to the investment in technical expertise and equipment is that an archive with a small collection should consider not having a laboratory at all. Such archives are well advised to pool their resources and have a joint technical service or work closely with an existing film laboratory. The individual archives will still, however, need to have on their staff at least one technically qualified person who can liaise with, and oversee the work carried out by, the laboratory.

1.2 Basic Equipment

1.2.1 Hand-winding Table

The two plate horizontal hand-winding table is the most important device used for the initial examination of the film and its condition. The feed and take-up spools of the plates should be able to accommodate different gauges, projection spools and cores.

The film is wound through by hand to allow a technical inspection to be carried out. At the same time, dirt can be removed and any damage to perforations etc. can be noted. In the printing laboratory, a similar table can be used for grading.

1.2.2 Footage Counter

A footage or metre counter should be built into the table to perform the important task of measuring the film.

1.2.3 Gloves

Gloves of a soft, white material, for example non-fraying cotton, should be available for use on occasions when it may be necessary to touch the surfaces of the film by hand. The use of gloves will prevent grease or harmful acids from the hands being transferred to the film and soiling or damaging the emulsion. The gloves should be changed at least once a day and whenever they become visibly dirty or become damp with perspiration.

One exception to this rule is when winding film with damaged perforations. If gloves are worn there is a danger of causing further damage to the film by catching the broken perforations on the cotton threads of the gloves.

1.2.4 Scissors

Scissors are required for repairing perforations and for preparing splices.

1.2.5 Brush

A soft brush is sometimes sufficient to remove particles of loose dust.

1.2.6 Scraping Knife

Scraping knives are needed to remove the emulsion and any protective layer when preparing splices or repairing perforations.

1.2.7 Splicers: 16 and 35mm

Splicers are needed for making or renewing splices. A bottle of film cement should be provided on the workbench as well. The quantity of cement used for a joint must be accurately judged, as any excess will spread beyond the join and spoil the adjacent pictures. There is a need to make splices by hand when repairing film that is very shrunk or which has the frameline in a non-standard position. Joins made by hand can be done in a manner in which the quantity of cement used is not critical.

1.2.8 Shrinkage Gauge

When working with old film it is very important to know the degree of shrinkage. Any carelessness here can lead to irreparable damage. Shrinkage measuring rods, on which the degree of shrinkage is read off a calibrated scale, are easy to use but imprecise. More exact measurements are obtained with a shrinkage gauge. With this tool, the film is laid in a channel and positioned by two precisely defined perforations onto two pins; one fixed and one moveable. The moveable pin is connected to a counter that shows the degree of shrinkage as an exact percentage.

1.2.9 Soft Wax Pencils

Soft wax pencils such as the "Chinagraph" brand should be used for marking film.

1.2.10 Magnifier

A ground glass screen, illuminated from below, and a magnifying glass, preferably mounted on a flexible arm, are needed to examine film. The screen and light source should be mounted in the winding table for convenience.

1.2.11 Film Cement

Film cement is needed for repairs to splices (see 1.2.7 above).

1.2.12 Solvents for Cleaning Film

WARNING: The use of solvents for hand cleaning film should be kept to an absolute minimum. It is preferable to clean dirty film in a special cleaning machine. If film has to be cleaned by hand, it is essential to provide an extract ventilator above the work table to remove hazardous fumes.

Solvents Available Risk to User
(Because of Toxicity)
a. n-Butyl Chloride Low
b. Cyclohexane* Low
c. Cyclopentane* Low
d. Freon 113 Low
e. Heptane* Low
f. Hexane* Low
g. Methylcyclohexane* Low
h. 1,1,1-Trichloroethane Low
i. Trichloroethylene High
j. 2,2,4-Trimethylpentane* Low

* Very flammable substances.

Carbon Tetrachloride is extremely dangerous and is banned.

1.2.13 Film Cans

Film cans made of metal or plastic such as polycarbonate and polyethylene; not poly(vinyl/chloride) (PVC) should be use for long term storage of film. Cardboard cartons are unsuitable for this purpose as they absorb moisture and may have a high acid and peroxide content.

1.2.14 Film Material

Regular developed and unexposed film material can be used for the repair of damaged perforations. It is important that the pieces of film used for repairs are preshrunk to the same degree as the film being repaired. If this is not done then the perforations will not match and subsequent differential shrinkage may cause the film to buckle.

1.2.15 Film Bin

When working with film, it may be necessary to unwind considerable lengths into a film bin. The bin consists of a frame that holds a bag made of lint-free fabric.

1.2.16 Card Indexes

Each film store should have both of the following card indexes:

a. A technical card index, giving all the necessary data and the results of all tests carried out on each film.

b. A location card index that keeps track of the location of every film at all times.

These records can also be kept on an electronic data base. The keeping of such records, in whatever form, is vital.

1.3 Additional Equipment for More Advanced Archives

1.3.1 Editing Table

The film editor's most important piece of equipment is the editing table. It is a universal table that can be used for viewing, for running film in synchronism with sound-track and for editing. If a table is only used to view combined film ie. the sound and picture are on the same carrier, two plates are sufficient.

1.3.2 Synchronizing Table for Multiple Strips

Synchronizers are used to prepare film for printing or for comparing two or more films. With a synchronizer, the negative and print or two or more prints can be run in synchronism, the start marks can be checked, sound-tracks and pictures can be viewed and work done with trial copies. The visible picture is only the size of the frame. The table cannot be switched from one gauge to another as needed but tables that accept two 16mm and two 35mm reels are available.

The table can be driven by hand or by electric motors and, in the latter mode, the speed can be continuously varied as well as running at the correct synchronous speed. The sprockets that drive the various strips can be connected and disconnected from the footage or metre counter as needed. Loudspeakers for sound replay can also be built in.

1.3.3 Two-Screen Viewing Table

Two-screen viewing tables permit two reels of film to be run in parallel to allow technical comparisons to be made between negative and positive or between two prints of the same film. They are particularly useful for the task of re-editing old films to restore them to the correct sequence and to the original length. An editing table with several film strips, with both optical and magnetic sound, can also be used for synchronization.

1.3.4 Motorized Winding Table

The motorized winding table with counters for feet or metres performs the same function as the hand winding table. Its speed is continuously variable and makes the film examiner's work easier.

1.3.5 Film Washing Machine

Fine scratches on the emulsion side of the film may be removed by causing the emulsion layer to swell. Small developing machines are suitable for this purpose if the developer is removed and the first tanks are filled with baths to soak the emulsion. A developing machine can also be used for rinsing the film with clean water in place of the developer. In tropical areas, this water may have to be pre-cooled as its temperature should, ideally, be kept below 20EC and never allowed to rise to 25EC. If the relative humidity of the air is too high, dehumidified air has to be used to supply the attached drying cabinet.

Modern rinsing machines often have provision for additional cleaning by means of a buffer system rotating under the water. New machines should be ordered with a friction drive transport system for the film. This will permit the machine to be used for all formats up to 35mm. A water filter may prove economical in recycling the used liquid. The hardness of the water should be kept as low as possible to prevent dry spots forming on the film. In the case of films which have suffered invisible decomposition of the base, washing may completely remove the emulsion layer.

A film should NOT be washed if any of the following apply:

i. A nitrate film has failed an emulsion solubility test carried out on at least one frame per roll of film.
ii. The film is to be treated for fading.
iii. It is a colour print made by a dye transfer process eg. Technicolor prints.

1.3.6 Cleaning Machine

There are two main types of cleaning machine in existence: ultrasonic and rotating buffer systems. The best results are obtained by using both systems in combination. A recycling system for the used solvents must be installed with the cleaning machine (see 1.2.12 for information about solvents).

1.3.7 Film Polishing Machine

This is used to eliminate damage, such as light scratches on the base side of the film, by polishing and matting the film between rollers of optical glass. Acetone is usually used in this process and adequate ventilation is essential for the machine and the surrounding work area.

1.3.8 Projector

All normal theatrical projectors can be used and are available for all the common, present-day standards. Dual gauge projectors (16/35mm or 35/70mm) are also available. Old, silent films, shot at speeds lower than 24 frames per second, must be projected at the original speed.

Double headed projectors are required for simultaneous projection of films with separate sound tracks.

Film intended for permanent preservation must never be used for projection.

1.3.9 Densitometer

A densitometer is an optical instrument that very accurately measures the optical density of details of a sample of film. The values obtained are important for maintaining output at a constant quality during processing at the laboratory and for assessing loss of density in recordings that are being preserved for long periods of time.

Even those archives that do not have their own printing laboratory should acquire and use a densitometer to check their colour and black and white films in storage. Loss of density during archival storage is a sign of the decay of the film. If possible, the densitometer should have a digital readout.

1.4 Additional Equipment for Fully Equipped Archives

1.4.1 Introduction

A fully equipped archive differs from a well equipped one in so far as it is able to copy particularly difficult archive material that cannot be handled in commercial laboratories which lack the specially adapted machinery required. The special problems of this material include extreme shrinkage or damage and outdated or rare formats and colour techniques. In general, it is possible to modify and adapt standard equipment to meet the specific requirements of such material.

One welcome modern development is the wet printer. This produces acceptable copies of a scratched and damaged original by a process of copying in liquid.

Modern printers may have a range of special lamphouses for copying colour and black and white film. Colour analysers must be used for these machines.

1.4.2 Colour Analyzer

Preparing a colour film for printing involves checking the colour balance as well as controlling the printer light intensity. The colour analyzer is used for grading of films.

1.4.3 Printing Machines

For copying film material, several different types of printing machine exist:

a. Contact Step Printers

The film to be copied and the raw, unexposed film are moved, frame by frame in direct contact with each other, past the printer's picture gate by means of a claw. This type of printer does not alter the picture format. It can handle shrunken original film, up to about 1.5% shrinkage, if appropriate sprockets are used and the claw's dimensions are suitable for the degree of shrinkage ie. they will not damage the perforations. These machines are suitable for archival use and give great picture sharpness and steadiness. There are wet gate systems available that can be adapted to fit contact step printers.

b. Optical Step Printers

The original and the raw film are moved in opposite directions frame by frame by a claw. Between them is a lens that can be adjusted to vary the size of the transmitted image to enlarge or reduce or to retain the original size. Because of its versatility, this type of printer is very suitable for archival use. It permits reduction and enlargement printing to be carried out for all formats. Moreover, with optical printers it is possible to carry out anti-scratch printing, ie. wet printing, by which means new prints made from normally scratched originals are scratch-free. With this type of printer, it is also possible to adjust the claw stroke to cope with badly shrunken original film.

c. Continuous Printers

These are designed for the rapid production of large quantities of prints. They are used by commercial film laboratories. Technically they are distinguished from step printers by the method of film transport. The films are moved past the exposure slit, not intermittently by a claw, but by a high precision sprocket wheel that rotates continuously. Feed and take-up is by means of normal filmguide rollers. These machines may work at speeds as high as 2000-3000 feet per minute.

As with step printers, there are contact machines and optical machines. While contact machines produce prints of the same format, continuous optical printers are used almost exclusively for reduction printing of optical sound tracks from 35mm to 16mm. There are also special continuous printers available for the copying of archival material. In most cases, damage to the original material does not require repairing before copying. Many continuous printers can be supplied as wet print machines.

d. Special Effects Printer

These are very versatile. They can do everything described in paragraph b. above, and more. They were designed for use in film production and, technically, they consist of a projector and a camera mounted on an optical bench. These machines operate very slowly. It is unlikely that an archive will make full use of all their capabilities eg. making wipes and dissolves. Their value to an archive is, however, undoubted. Wet print versions are also available.

1.4.4 Developing Machines

These are used to develop exposed film. Whereas older models are provided with 35 or 16mm sprocket drives, the newer models have friction wheel transports and can accommodate any format up to the width of their wheels. The required capacity of the developing machine will depend on the output of the printing machines supplying the exposed film for processing. In general, it is better to have separate machines for positive and negative and for black and white and colour film.

In tropical climates, close attention must be paid to the temperature of the developing liquids as the cooling water may, itself, be too warm. Replenishment of the developer and the fixing bath must be harmonized with the speed of the passage of the film and with the film formats being processed. The replenishment supplies must be precisely controlled.

An important element in the operation of all processing machines should be the recycling of the various developers and the recovery of silver from the fixing solution. This is not just for economic reasons but for ecological ones as well.

1.4.5 Chemical Laboratory

Any archive that has its own printing laboratory will also need a chemical laboratory where the mixing of developing baths etc. and the relevant analyses can be carried out. The analysis methods must be undertaken in accordance with the chemical manufacturers' recommendations. The laboratory's basic equipment may need to be supplemented by special pieces of apparatus as necessary.

Those archives that do not have a printing laboratory may still require a chemical laboratory if they carry out tests such as measurement of colour density, nitrate/acetate tests, artificial ageing tests for nitrate and residual thiosulphate tests on a regular basis.

1.4.6 Optical Sound Projector

Generally speaking, sound tracks and the film that carries the images are treated separately because they require different techniques. Films often have optical sound tracks and, therefore, need a special sound head. Its lens should be able to move across the full width of the sound track and be provided with a reading or scanning device to avoid accidentally reading perforations and frame lines. If the unit has a wet system, then scratches on the base and emulsion can be minimized.

1.4.7 Sound Mixing and Processing Equipment

These are used to treat sound information from old films eg. the removal of hums and the alleviation of noise.

Generally speaking, sound tracks and the film that carries the images are treated separately because they require different techniques. Films often have optical sound tracks and, therefore, need a special sound head. Its lens should be able to move across the full width of the sound track and be provided with a reading or scanning device to avoid accidentally reading perforations and frame lines. If the unit has a wet system, then scratches on the base and emulsion can be minimized.

1.4.8 Magnetic Sound Recorder: 16/17.5/35mm

The magnetic sound recorder is used to record sound on tape. The recorder and projector may be connected mechanically or electronically to synchronize their speeds.

1.4.9 Optical Sound Camera: 16/35mm

The optical sound camera is used to record sound on film.

1.4.10 Microscope

A microscope is useful for detailed examination of older film materials which the archive intends to preserve. Early signs of damage such as fungus growth, the action of bacteria and minute perforation tears, which may prove catastrophic in the long-term if not countered, are more easily detected with a microscope than with a magnifying glass.

If wafer-thin, diagonal cuts are made in the emulsion, it is possible to see under the microscope if the layer adhesion is still intact.

Archives with their own printing laboratory will find a microscope indispensable for measuring the picture steadiness of the printer. Unsteadiness introduced by printing is usually detected when projecting the copy.

1.4.11 Sensitometer

The sensitometer consists of a fixed printing light which is closely defined as to intensity, exposure time and colour temperature. It is used in conjunction with a standard grey scale which is placed with the raw film in the sensitometer when it is exposed. At the laboratory, the exposed strips are developed, fixed and dried in a small developing machine with standardized baths. They can also be clipped to exposed film tests or films and developed with them.

The manufacturers' instructions must be followed exactly throughout the process. By comparing the new copy of the grey scale with the standard, the raw film stock can be assessed to see if it meets the required optical specifications. Control over the development in subsequent processing can also be maintained.

If the archive does not have a sensitometer, it can have the necessary grey scale supplied by the raw film manufacturers.


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