GB1600861A - Cinematograph film and method of exposing the same - Google Patents

Description

(54) CINEMATOGRAPH FILM AND METHOD OF EXPOSING THE SAME (71) We, VIRECO, A.G., a Swiss Company, of Bahnhofstrasse 94, 8001 Zurich, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a photographic film carrying a cinematograph record and a method of exposing the film to make the record. British Patent Application 48442/76 (Serial No 1596276) describes a cinematograph projector for projecting film in a continuous (non-intermittent) movement. A practicable system is made possible by the use of an extremely small film frame size.

The projector includes a scanning device which is synchronised with the movement of the frames by electrical synchronising pulses derived optically by the passage of photographically printed synchronising marks past a photo-detector.

Because of the high magnification required for projection of the very small film frames it is important to ensure that frame synchronisation is as accurate as possible, since the effect of any discrepancies will be magnifies considerably. In making the film record it is convenient to print the film in an automatic, continuously running, printing from a master negative. The master negative is prepared complete with synchronising marks in an intermediate stage from the master film stock which may be conventional, sprocketed, 35 mm or 16 mm film.

In the intermediate stage, it is best to employ an automatic intermittent-movement printer, since this allows the master film stock of conventional format to be copied frame by frame. However, it is found that because of minor mechanical tolerance variations in such printers, the spacing of the film frames may vary a little. Such small variations are not important when the printed film is intended for conventional intermittent projectors but the variations have been found to be significant for continuous-motion projection, particularly when very small frame sizes are employed.

Conventional printing processes punch sprocket holes in the film in a separate operation from the exposure of the frames. It has been found that the equivalent process of separately photographically exposing synchronising marks for continuous-motion film is not satisfactory since variation as little as 0.0003", for example, in the film frame spacing, arising from mechanical tolerances in the printer or because of film stretch or shrinkage, produce small but serious discrepancies between the positions of the synchronising marks and the pertinent film frames.

In accordance with one aspect of the present invention each optical synchronising mark of a continuous-motion cinematograph film is obtained by photographic exposure when the film frame pertinent to that mark is exposed.

In accordance with another aspect of the invention there is provided a continuousmotion cinematograph film having a series of film frames and a parallel series of photographic synchronising marks, each mark pertaining to a particular frame, each mark being made by photographic exposure when the pertinent frame is exposed. This allows the distance of each mark from its pertinent frame to be exactly fixed, even if the frameto-frame distance varies slightly.

The film in accordance with the invention may be the final print for projection or an intermediate negative. In producing the intermediate negative the method of the invention will generally add synchronising marks by photographic exposure at the time the pertinent film frames are printed. When printing the final print from the intermediate-negative, the synchronising marks accompanying the film frames are printed simultaneously therewith.

Another way of providing a print for projection is to expose a film in a ciné camera. In accordance with the invention film exposed in this way is provided with synchronising marks exposed simultaneously with exposure of the film frames.

Although it is preferable to have a synchronising mark for each frame, it is not necessary; synchronising marks may instead by provided for only every second, third, or tenth (for example) frame. The projector will operate on a free-running basis between synchronising marks and be brought back to absolute synchronism with each mark.

Preferably each synchronising mark is the edge between an exposed and a non-exposed part of the film. The photo-detector of the projector may be designed to operate on the transition from a black to a transparent part of the film or vice-versa. Thus, the synchronising track on the film may appear as transparent "holes" in a back strip or as black blocks in a transparent strip. In either event it is the leading edge (having regard to the direction of movement of the film) of the "hole" or block which is the synchronising mark.

While the invention may be used to expose single-track film, another film format is as shown in Specification No. 1596276 where twin film frame tracks are provided and a common synchronising track is situated between the two film frame tracks. In this case the leading edge of a "hole" or block for one direction of movement of the film is the trailing edge for the other direction of movement. The two edges will be exposed separately, one during the exposure of the pertinent frame in one track and the other during the exposure of the pertinent frame in the other track.

However, experiments have shown that satisfactory synchronisation can be achieved with extremely small synchronising marks, perhaps 0.1 mm or less in width. This allows a twin track of synchronising marks to be used even on the very small film format described in Application No. 48442/76 Serial No 1596276. This offers the advantage that each of the two parallel film tracks can have its own independent synchronising tracks and relieves the requirement that the film frames on the two tracks should be at least approximately aligned.

The invention will further be described with reference to the accompanying drawings, of which: Figure 1 is a schematic diagram of an automatic printer employing the invention; Figure 2 is a schematic view of a continuous multiple printer for printing films from the intermediate negative produced in the printer of Figure 1; Figure 3 is a schematic view illustrating the format of the intermediate negative produced in the printer of Figure 1: and Figure 4 is a diagram of an alternative film format.

The intermediate negative film 2 is printed with two parallel tracks of film frames, the first of which is shown being exposed at 18 in Figure 1.

The films are driven intermittently in step by a drive mechanism in the direction shown by the arrows. The drive mechanism is coupled to drive a sprocket wheel (not shown) which engages with the film 1 and a capstan wheel 4 which frictionally engages with the film 2 by pinching the film against a pinch roller 5. The films are moved frame by frame and stopped intermittently at each frame position. When the frames are in position, the mechanism operates a shutter 6 which exposes the film 2. The films are then moved to the next frame position. It will be appreciated that because of the reduction in frame size, the extent to which film 2 moves for each frame is less than that for which film 1 moves.

For exposing the film frames, light is projected from a projection lamp and condenser lens system (not shown), through the film 1 and is focussed by a projection lens 8 onto the film 2. A mask having a frame aperture 11 defines the frame size for the film 2.

Between the film 1 and the shutter 6 is a beam-splitting prism 9. Prism 9 allows light from a synchronising mark mask 10 to be added at the edge of the film frame to the light passing to lens 8 from the mask aperture 11. Thus, there is printed on the film 2 a synchronising mark adjacent each film frame. Each synchronising mark is exposed through the shutter, simultaneously with the film frame to which it is pertinent. It is to be noted that the film frame to which a synchronising mark is pertinent is not necessarily the adjacent frame.

The mask 10 receives light from a lamp 15 and is arranged to print opaque synchronising marks on the intermediate negative film, these being produced as transparent marks on the final prints. The position of the mask 10 in the direction of film movement determines the position of the synchronising marks with respect to their pertinent film frames. With the arrangement shown in Figure 1 the synchronising marks would be produced adjacent the pertinent film frames.

However, the required relative disposition of synchronising marks and film frames will depend on the disposition in the projector of the film viewing aperture and the synchronising aperture. In one form of the projector the distance between the synchronising aperture and the film viewing aperture is approximately equal to four frame pitches. However, it is expected that this distance more usually will be about one frame pitch.

Referring now to Figure 2 there is shown a printer for printing films from the intermediate negative 2 of Figure 1. The intermediate negative is run continuously in the printer and collimated light is directed through the film 2, through a projection lens 30, and a splitter 31 to a film 32. The beam-splitter splits the image from the film to four parallel film tracks on film 32. Because of the scale reduction in the printer the film 2 travels four times as fast as film 32.

Film 32 passed over a roller 33 and through a series of processing tanks 34 to develop and dry the film. A magnetic striping unit MS applies magnetic stripes 35 to the film at the edges of each pair of film frame tracks. These will carry the sound-tracks for the film. A slitter 36 then slits the film 32 into four parallel strips 37, each carrying a double-track film with sound-tracks. The sound-tracks may be recorded before or after slitting.

It will be appreciated that the final film prints 37 will have their synchronising marks exactly the correct distance with respect to the pertinent film frames because (a) the synchronising marks on the intermediate negative 2 are exposed with the pertinent film frames and (b) of necessity, the synchronising marks on the prints 37 are exposed with the pertinent film frames. Thus, the effects of machine tolerances and film stretch, etc, may manifest themselves in slight variations in film frame spacing, the associated synchronising marks will reflect the same variations.

Figure 3 shows the film format in respect of the intermediate negative 2. The film has, at each edge, space 16, 17 for a magnetic stripe on the film print each of which is for carrying two soundtrack channels for providing stereophonic sound. Soundtrack space 16 is associated with a film constituted by a track 18 of photographic frames and soundtrack space 17 is associated with a film 19 of photographic frames.

It is to be understood that the present description relates to the stage of exposure of the film 2 and accordingly the film frames and synchronising marks will not actually be visible at this stage, but will be visible when developed. Nevertheless, for convenience, reference will be made to the frames and synchronising marks as if they are visible.

The synchronising track 20 is constituted by alternate transparent and opaque patches, or "holes" and blocks. The synchronising system in the projector responds to the passage of the leading edge (e.g. 12) of a block. Each leading edge is pertinent to a particular film frame. Furthermore, it is to be understood that the leading edge of a block when the film moves in one direction is the trailing edge when the film moves in the other direction. Accordingly, examples in Figures 1 of leading edges and pertinent frames are: Edge 21 pertinent to frame 22; edge 23 pertinent to frame 24; edge 25 pertinent to frame 26, and so on.

As shown in Figure 2, the first track 18 of the film has been exposed and the appropriate synchronising marks (for example, 25) have been made. In the condition shown in Figure 3, the second track 19 of the film is being exposed.

Each block 27 of the synchronising track 20 is approximately half the length of a frame. The blocks are photographed by exposure through the aperture 10. The aperture 10 is approximately 1 ofthe full width of each block 27 so that in the first exposure for track 18, the exposed blocks are only i the full length. However, their leading edges (in the relevant direction) are the appropriate distance from the pertinent frames. The function of the second exposure illustrated in Figure 3, is to define the leading edge in the other direction, the position of this leading edge being pertinent to the appropriate frames in the track 19. It is only the positions of the two edges of the blocks which are important and it will be seen that the mid part of each block is exposed twice, once for each track.

In the final film print the dimensions are such that the film is 8 mm wide; each of the film tracks is 2.6 mm wide; and the frame pitch is 2.117 mm. Between the two film tracks the synchronising track 20 is 0.3 mm wide.

Referring now to Figure 4 there is shown an alternative film format where the synchronising track 20 is a double track, 20a, 20b. Track 20 a corresponds to film track 18 and track 20b corresponds to film track 19.

Each track 20a, 20b is 0.1 mm wide. The advantage of this arrangement is that there is no need to ensure that the frames of each film track are even approximately aligned with each other. The synchronising marks on the film of Figure 4 are made in the simultaneous explosive manner as described with reference to Figure 1.

It is to be understood that the invention is not restricted to the details of the foregoing description made with reference to the drawings. For example, the intermediate negative 2 may be of any convenient size, perhaps 8 mm or 16 mm film instead of 35 mm. Also, more or less copies than four may be made in the printer of Figure 2.

WHAT WE CLAIM IS: 1. A method of exposing a cinematographic film for continuous motion projection, the method consisting in exposing a track of film frames to make a cinematograph record on the film and exposing a track of optical synchronising marks parallel to the film

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. Referring now to Figure 2 there is shown a printer for printing films from the intermediate negative 2 of Figure 1. The intermediate negative is run continuously in the printer and collimated light is directed through the film 2, through a projection lens 30, and a splitter 31 to a film 32. The beam-splitter splits the image from the film to four parallel film tracks on film 32. Because of the scale reduction in the printer the film 2 travels four times as fast as film 32. Film 32 passed over a roller 33 and through a series of processing tanks 34 to develop and dry the film. A magnetic striping unit MS applies magnetic stripes 35 to the film at the edges of each pair of film frame tracks. These will carry the sound-tracks for the film. A slitter 36 then slits the film 32 into four parallel strips 37, each carrying a double-track film with sound-tracks. The sound-tracks may be recorded before or after slitting. It will be appreciated that the final film prints 37 will have their synchronising marks exactly the correct distance with respect to the pertinent film frames because (a) the synchronising marks on the intermediate negative 2 are exposed with the pertinent film frames and (b) of necessity, the synchronising marks on the prints 37 are exposed with the pertinent film frames. Thus, the effects of machine tolerances and film stretch, etc, may manifest themselves in slight variations in film frame spacing, the associated synchronising marks will reflect the same variations. Figure 3 shows the film format in respect of the intermediate negative 2. The film has, at each edge, space 16, 17 for a magnetic stripe on the film print each of which is for carrying two soundtrack channels for providing stereophonic sound. Soundtrack space 16 is associated with a film constituted by a track 18 of photographic frames and soundtrack space 17 is associated with a film 19 of photographic frames. It is to be understood that the present description relates to the stage of exposure of the film 2 and accordingly the film frames and synchronising marks will not actually be visible at this stage, but will be visible when developed. Nevertheless, for convenience, reference will be made to the frames and synchronising marks as if they are visible. The synchronising track 20 is constituted by alternate transparent and opaque patches, or "holes" and blocks. The synchronising system in the projector responds to the passage of the leading edge (e.g. 12) of a block. Each leading edge is pertinent to a particular film frame. Furthermore, it is to be understood that the leading edge of a block when the film moves in one direction is the trailing edge when the film moves in the other direction. Accordingly, examples in Figures 1 of leading edges and pertinent frames are: Edge 21 pertinent to frame 22; edge 23 pertinent to frame 24; edge 25 pertinent to frame 26, and so on. As shown in Figure 2, the first track 18 of the film has been exposed and the appropriate synchronising marks (for example, 25) have been made. In the condition shown in Figure 3, the second track 19 of the film is being exposed. Each block 27 of the synchronising track 20 is approximately half the length of a frame. The blocks are photographed by exposure through the aperture 10. The aperture 10 is approximately 1 ofthe full width of each block 27 so that in the first exposure for track 18, the exposed blocks are only i the full length. However, their leading edges (in the relevant direction) are the appropriate distance from the pertinent frames. The function of the second exposure illustrated in Figure 3, is to define the leading edge in the other direction, the position of this leading edge being pertinent to the appropriate frames in the track 19. It is only the positions of the two edges of the blocks which are important and it will be seen that the mid part of each block is exposed twice, once for each track. In the final film print the dimensions are such that the film is 8 mm wide; each of the film tracks is 2.6 mm wide; and the frame pitch is 2.117 mm. Between the two film tracks the synchronising track 20 is 0.3 mm wide. Referring now to Figure 4 there is shown an alternative film format where the synchronising track 20 is a double track, 20a, 20b. Track 20 a corresponds to film track 18 and track 20b corresponds to film track 19. Each track 20a, 20b is 0.1 mm wide. The advantage of this arrangement is that there is no need to ensure that the frames of each film track are even approximately aligned with each other. The synchronising marks on the film of Figure 4 are made in the simultaneous explosive manner as described with reference to Figure 1. It is to be understood that the invention is not restricted to the details of the foregoing description made with reference to the drawings. For example, the intermediate negative 2 may be of any convenient size, perhaps 8 mm or 16 mm film instead of 35 mm. Also, more or less copies than four may be made in the printer of Figure 2. WHAT WE CLAIM IS:

1. A method of exposing a cinematographic film for continuous motion projection, the method consisting in exposing a track of film frames to make a cinematograph record on the film and exposing a track of optical synchronising marks parallel to the film

frame track, each synchronising mark corresponding to a pertinent respective film frame, the synchronising marks being exposed in the same operation as their pertinent film frames are exposed.

2. A cinematograph film when exposed by the method of claim 1, the film being characterized in that each synchronising mark is an exact predetermined distance from its pertinent film frame, regardless of any variations in spacing of the film frames.

3. A film as claimed in claim 2 wherein the synchronising mark is the leading or trailing edge (having regard to the direction of movement of the film) of a transparent or opaque block on the film.

4. A film as claimed in claim 3 wherein there are two tracks of film frames, one track being projected when the film runs in one direction and the other track being projected when the film runs in the other direction; and a single track of synchronising blocks between the frame tracks, the synchronising marks being the leading (or trailing) edges of the blocks for one film track and the opposite edges of the blocks for the other film track.

5. A film as claimed in claim 2 or claim 3 wherein there are two tracks of film frames, one track being projected when the film runs in one direction and the other track being projected when the film runs in the other direction; and a double track of synchronising blocks between the film tracks, one track of synchronising blocks corresponding to one film track and the other track of synchronising blocks corresponding to the other film track.

6. A film printer for copying cinematograph film from conventional film stock on to a copy film in a format suitable for a continuous projector, the format having a track of film frames and a parallel track of synchronising marks, each synchronising mark corresponding to a pertinent film frame, the printer having projector means for exposing the copy film to images of frames of the conventional film stock, synchronising mark projector means for generating an optical image of a synchronising mark; and combining means which combine the frame image and the synchronising mark image so that the copy film is exposed to each synchronising mark image at the same time as the pertinent frame image.

7. A method of exposing cinematograph film in accordance with claim 1 substantially as hereinbefore described.

8. A cinematograph film substantially as hereinbefore described with reference to Figure 3 or Figure 4 of the accompanying drawings.

9. A film printer substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.