ITS REALIZATION

Technical field

The invention relates to a method applicable to additional processing of a cinematographic film strip for attaining various colour effects in different sections of the strip, whereby different physico-chemical technologies may be applied to each section without the necessity to cut the film into pieces.

Background of the invention

At around 1920, when only black-and-white film existed, several methods of additional colouring were in use in the manufacture of prints: toning, where a part of silver was transformed to a coloured substance; pickling, where silver was reduced to a colourless compound and subsequently combined with some special dyes, pickling dyes; and, finally, a method wherein the gelatine layer was uniformly coloured by a solution of a water-soluble dye. Today, these films are filed in archives all over the world; they are invariably made with a flammable, celluloid, substrate; in view of the limited life of celluloid films and the danger stemming from their flam ability it is at present necessary to produce their incombustible copies, to be filed in collections. In manufacturing the copies of such films one may

use any colouring process, where however all colour faults due to ageing are also copied. Another drawback consists in that the resulting colour print has only limited use for storing, since as a result of ageing, even if the film is stored in the dark, considerable colour degradation and, consequently, substantial deterioration takes place after a prolonged time period. Another immediately apparent drawback is that colour rendering, identical to that of the original, can be never achieved, since colour of the original is mostly due to a single dye, exceptionally two dyes, with a certain colour density and specific spectral characteristics, while the colour of the final print is due to mixing of three dyes, resulting in only approximate colour effect - each new copying process leads to additional degradation of colour rendering.

Another method in use consists in that a black-and-white positive copy is produced from the original by a black-and-white positive/negative process, the copy is cut to pieces according to the colour of the original, such pieces being then processed by procedures used for manufacturing the original or by tested procedures leading to identical colour effect. In comparison with the previous ones, this method brings about the advantage of considerably improved correspondence with the original, since each technology can be checked visually and spectrometrically and the result compared with the original. However, the main drawback of this method is its laboriousness, brought about by the necessity of cutting the film into individual pieces, their proper filing, separate processing and subsequent splicing, and also the fact that the resulting print contains as many splices as there are jumps in the colour rendering in the original: in a reel of film of length 500 - 600 m there are

usually 80 to 100 splices, but sometimes 150 or even more, and in each splice at least one original frame is missing. In screening splices represent the most stressed locations: prior to screening all splices must be checked as to their integrity and ability to pass through the projector, and repaired whenever necessary. Prints to be screened in cinemas are designated as class 4, a print entirely unsuited for screening already when containing 20 or more splices per reel, about 600 m. During storage in a collection - and this is the main destination of prints produced in this way - each splice represents a location of impaired integrity and uniformity of the strip and disturbed gelatine layer: most chemical and biological changes proceeding in the emulsion layer or in the substrate (ageing - chemical decomposition and moulding) start there. Another drawback inherent to this method consists in that it does not allow one to accomplish a continuous colour change, often required in some films.

Summary of the invention

Practically all drawbacks of the above processing procedures are put aside by the described method, wherein an uncut black- and-white strip is led through a processing machine where only those sections are contacted with processing baths, in which the required colour changes is to be achieved. It is also possible to ensure that all elements of the processed section are in contact with the bath for exactly the same time period

- a requirement fundamental for the attainment of the same change of colour along the given film section. In order to realize a continuous colour variation - a requirement sometimes, though not very often, met- it

is possible to arrange for individual frames of the processed section to be contacted with the bath for different time periods.

The film is contacted with the bath in the form of a "U- loop", freely hanging between two driving wheels, - plain or sprocket-wheels, which maintain a constant length of the loop. The film can either hang freely by its own weight or can be equipped with a stretching weight to ensure a more uniform passage. The loop length can be controlled at will and the film can be thus lowered to at the beginning of the processed section, or raised from at the section end, the bath, because each of the two driving wheels - one before, the other behind the bath - can rotate and stop independently with regard to both direction and speed. It is naturally equally possible to ensure that both wheels rotate at identical speed, so that the immersion depth of the film remains constant, the film passes through the bath at constant velocity, and each frame is thus contacted with the bath for the same time period.

At the beginning of the processed section the film is lowered into the bath by allowing only the inlet wheel to rotate, while the outlet wheel is stationary.

As a result the film loop, previously stretched above the bath surface, begins to lengthen and at a given moment is immersed into the bath. By means of an exact adjustment in advance one may ensure that the point of the required step colour change caused by immersion into the bath be located exactly at the boundary between the bath surface and air. After a time period - preset to correspond with the residence .time of the processed section in the bath - has elapsed, the outlet wheel starts to rotate synchronously with the inlet wheel. To end the processing of the given scene the rotation of the inlet wheel is stopped exactly at the moment when

the end of the processed section approaches the bath surface, while the outlet wheel continues to rotate. The film is thus raised from the bath at the same velocity and the required colour boundary is attained. It is obvious that the entire processed film section is contacted with the bath for the same time period

(including the frames at the section beginning and end, where the film has been lowered into and raised from the bath, respectively; accordingly, a uniform colour change has been attained. It is similarly possible to achieve a continuous colour variation by changing the speed of rotation of the two wheels in such a manner that the speed increases in places where the colour should be weaker, but decreases in places where a strengthening of the colour effect is required.

It is also of advantage if - at the moment the film leaves the bath - the inlet driving mechanism starts to rotate in the opposite direction and with speed matching or even higher than that of the outlet mechanism; this prevents run-down of the sticking liquid to frames that should not have been affected.

The invention also relates to an equipment capable to realize the above processing method. The equipment in essence consists of at least one cell with the processing bath and at least two driving mechanisms, inlet and outlet, warranting the required passage of the film. The required motion can be ensured by two step motors fed by two independent sources of impulses, capable of mutual synchronization. It is also possible to realize the above requirements by a mechanical drive, where a synchronous motion can be achieved by means of suitable gears, and the motion of the two mechanisms at different speeds or with a different sense of rotation can be realized by attaching one of them to a second, auxiliary drive.

The advantage of the processing by means of the above equipment is that the film is handled by technologies that faithfully mimic the colour effects existing in the original - in fact, on might achieve an indistinguishable resulting effect. An arbitrarily large number of processing procedures and their variations may be employed for handling the individual film sections, depending on the number of colour effects in the original; at the same time, the film strip is processed as a whole, without cutting and subsequent splicing, whereby the processing is considerably simplified and the resulting print does not contain any splices. Because of all these characteristics the product can be easily kept on file, since dyes originating from silver by chemical reactions are in effect inorganic compounds that do not undergo decomposition, and the organic dyes used also do not decompose spontaneously, in contrast to dyes used in colour films - they moreover often tend to protect gelatine against biochemical attack, and this is further assisted by the integrity of the strip (no splices) .

To simplify the operation of the above equipment it is also advisable to include in it more than two independently controlled mechanisms, thus allowing the film to pass through several baths simultaneously, or to select only some and skip the others, thus avoiding the necessity to change the contents of a cell or the cell itself prior to each change in the processing method.

With an equipment containing several cells it is also possible to use the end cells for washing and drying- purposes; these operations might be otherwise accomplished separately in an auxiliary system, whose speed of operation is derived from the velocity of the processed film. Such systems are common to machines processing 35 mm films and they do not form a part of

the present invention.

It is also apparent that in equipment with more than two driving wheels and more cells than one the wheel which operates as inlet wheel for one cell is at the same time an outlet wheel for the immediately preceding cell.

Brief description of the drawings

The invention will be illustrated by a drawing, where Fig. 1 represents the equipment for realization of the method according to the present invention; the equipment contains three cells for chemical baths so that it can serve for carrying out up to three different chemical operations without the necessity to change baths; by means of four independently controlled wheels the strip can be lowered into any cell without it coming into contact with baths in the remaining two. Figure 2 shows the wiring of one step motor (identical for all step motors used) .

Detailed description of the preferred embodiments

The equipment according to Figure 1, containing four independently controlled driving mechanisms, consisting of 35 mm sprocket wheels 1 , 2_, 3_, and 4_, each with four teeth; each is driven by its own step motor _. 5, -6, -1_, and 8.. The driving mechanisms are situated above the cells with chemical baths 9., _\__\, and _______ ith film passing from the left to the right, wheel 1 is the inlet wheel for cell 9., 2. is the outlet wheel for the same cell and simultaneously the inlet wheel for cell lfJ, etc. All four step motors are wired in the same way

- see Figure 2. Step motors with five inlets are used; these can be connected via a quintupolar switch to one of two independent sources of driving impulses ,14., 15.

The device operates as follows. If the strip is to be processed in cell 9_, motor 5. is connected to source 14. motors _5 , , and 8. to source 15 _. . A weight 13, consisting of a cylinder whose width is by several millimetres smaller than the cell width, is placed between wheels 1 and 2. onto the film to be lowered to the cell. Only source .14 _. begins to send the action impulses - wheel 1_ rotates, the remaining wheels are stationary, since source 15. does not send any impulses, thus blocking the rotary motion of motors 6., , and 8.. After a preset processing time source 15 begins to send a series of action impulses, with the same phase and frequency as source 3-4.. This state is preserved until the end of the processed section approaches the surface of the bath in the cell. At that moment source 14 discontinues sending impulses to motor 5. and wheel 1 stops. The film continues to pass through the bath with the same velocity as before; at the moment the loop raises above the level of the liquid, source 14 begins to drive motor 5. in the opposite direction ,by changing the phasing of the motor, and continues to do so until the film becomes stretched between wheels .1 and 2., when both drives - wheels are switched off. By removing the weight the processing of this section is finished.

Methods of processing in which baths in cells .10. or 11 are used are analogous - all inlet motors are controlled by source .14., outlet motors by source 15.