Principles of Duplication

Duplication is the most important of all the different steps of preservation and restoration.

It is the one that needs quality control and checking at the best.

In order to carry out duplication of archive films it is essential to understand the films and procedures available for modern duplication, since these films are the only specialised stocks available. In the past almost all manufacturers made specialised duplication films, but today it appears that only Kodak will continue to sell colour and black and white duplication films and will shortly be the only source of any motion picture black and white print film.

Archive film

Desirable attributes

Problems in Duplication

Equipment for duplicating

More

Modern duplication practice

The reasons for duplicating operations in modern conventional motion picture production are usually as follows:

1 - A finished production may require a number of special effects such as fades, lap dissolves, wipes, etc., and these are most conveniently made by using duplicating steps. The duplicated section with the special effect is then cut into the final cut negative.
2- Duplicate negatives may be required as insurance against total loss of the valuable camera original because of abrasion or other damage caused by improper storage or handling.
3. Duplicate negatives are frequently needed for shipment abroad for foreign release printing.
4. Reduced or enlarged duplicate negatives are economical intermediates when the camera original is larger or smaller than the final release print.
5. In making reduction [e.g. 16mm] prints from black and white or colour reversal originals, the preparation of internegatives offers economic advantages when larger quantities of prints are needed in comparison with making prints onto another reversal film.

Archive film duplication

In archive film restoration, duplication is carried for slightly different reasons

To preserve the image,
To enable the image to be presented in the cinema without damage to the original.
To attempt to recreate the original image in a form approaching that of the original, eliminating the visual effects of damage, shrinkage, fading and decomposition. This process is commonly called "restoration". In some cases of restoration the objective may be to "simulate" the original image without necessarily using materials or techniques that in any way resemble the original film or photographic principle. The Desmetcolor method of restoring tinted and toned films, for example, uses modern colour print stock and a unique exposure system.

It should be realised that the duplication materials on the market today, and those in the past, have been originally designed for quite different purposes to that of restoring archive film. A modern duplication film has been designed to duplicate a modern camera original film, not those of the past. Consequently, archive laboratories use modern materials in a manner that are frequently not as the manufacturer intended. Nevertheless, the setting up principles and procedures do not, and should not, depart from those of modern duplication, even though the contrast aims or density aims may not be the same.

Desirable attributes of duplicate and intermediate images

A duplicate negative, or any other duplicate element, is only a means to an end. The prime requirement is that it will have characteristics suitable for producing prints whose quality level is as close as possible to prints made from the original negative. This means that the tonal gradation, overall contrast, hue and saturation of the colours [in the case of a colour material], definition and graininess of the print made from the duplicate negative or intermediate must be as close as possible to that obtained in a direct print.

A common misconception is that a duplicate negative should appear visually and densitometrically like the original negative. Although this might be very desirable for a number of practical reasons, the materials used in the duplicating operations impose certain limitations, which make it impossible to achieve. Duplicate materials may have different base densities or different curve shapes or, in the case of colour, different dyes and masking. As a consequence, when original negatives are intercut with duplicate negatives, adjustments of the printer light intensity [and colour balance] must usually be made during final printing to give satisfactory prints from each. Obviously, the required changes must be within the range of light intensity and colour balance adjustments available in the printer to be used while still allowing for normal scene-to-scene corrections to be made. In almost every instance correctly exposed duplicate negatives, whether black and white or colour will normally have higher image densities than the original negative and will require increased printer exposure [and possibly some colour grading changes in the case of colour duplicates].

Problems in Duplication

1 Duplicating materials have a rather low inherent speed or sensitivity, generally in order to achieve as fine a grain and as high a sharpness as possible
2 In some production situations, laboratories may feel that it is necessary to depart from optimum tone reproduction. For example, a thin duplicate negative may be prepared to be intercut with a thin camera negative in order to minimise colour grading and intensity changes, or a thin printing master may be prepared for use on a printer having insufficient light intensity. This common procedure invariably leads to a loss in quality of the final print by introducing serious tone compression. This requirement quite frequently produces a better match with an original if the original is a rather tired colour release print than scrupulously following the rules. From this it can be seen that laboratories now, and in the past, frequently bent the rules to blend duplicate sections with the original or to minimise the grading effort needed.
3 A certain amount of variation between different batches of duplicating materials as well as variations in the process and printer may introduce some problems, especially when a colour duplicating film is used for making both colour master positives and colour duplicate negatives. This situation calls for careful testing of raw stock and strict control of process and printer variables to prevent losses in quality of duplicates.
4 Most film stock manufacturer's used to make duplicating materials for black and white use, called "Fine Grain" materials by Eastman Kodak, but recently most of these have been withdrawn from the market as black and white film is not widely used today.
5 Three general systems of colour duplication are still currently available, and the Eastman Kodak stocks are, again, those most used. Two of these are systems starting from a colour negative film and the third from a positive, such as a release print or a reversal original. Eastman Kodak devised all and although other film stock manufacturers also produce similar materials.
6 Specialist archive laboratories also use camera negative films for some duplication purposes because the colour and contrast characteristics of some just happen to be suitable for a special purpose.

Equipment for Duplicating

An intensity scale sensitometer having an intensity level and exposure time close to the conditions used in the printer [for example, the Kodak High Intensity Sensitometer type 6] is essential for the old but accurate 2-point system of duplication. Silver or carbon step tablets having a density range of 3.00 and density increments between steps of 0.15 and 0.20 are the most commonly used. The LAD system does not require the use of any sensitometer but is limited to the simpler duplication routes.

The densitometer used for duplication work is critical, and the choice of filter or filters will depend on the film to be measured and, above all it's eventual use. The Chapter on Control contains this information. In most other respects, for example, the choice of printer and grading equipment is the same as for any archive printing. However once the initial printing from the archive film has been done the later stages of duplication do not need specialist printing equipment, capable of handling shrunken film, and conventional equipment is used.

Terminology

Processes