WO1996033443A1

WO1996033443A1 - Color restoration process

Info

Publication number: WO1996033443A1
Application number: PCT/US1995/009089
Authority: WO
Inventors: Peter Kuran
Original assignee: Visual Concept Engineering
Priority date: 1995-04-20
Filing date: 1995-07-19
Publication date: 1996-10-24
Also published as: AU3135695A

Abstract

A process for restoring motion picture color negative film, which has faded over time. The original negative film is used to produce autopositive film and interpositive film. Using a blue filter, the original negative film is photo-chemically combined with the autopositive film to produce a yellow covermatte. Finally, using a slightly blue filter, the yellow covermatte is photo-chemically combined with the interpositive film to produce a restored negative film.

Description

COLOR RESTORATION PROCESS

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates generally to processes and apparatuses for restoring color film, and, in particular embodiments, to a process for restoring color of motion picture color negative film.

2. Description of Related Art Color negative film has been a popular recording medium for decades. However, color films, especially those produced in the early stages of color film technology, tend to fade over time. For color image restoration processes, this is especially problematic with motion picture color negative film, wherein thousands of images may be found on a single reel of film. Significant fading of motion picture color negative film has been known to occur in as little as ten years. Fading tends to occur primarily in the blue layer and somewhat in the green layer. The unstable blue layer often fades such that the highlights and shadow areas (D-Max and D-Min) are close to each other in density and present a false color of the original image. So, for example, a color negative from the 1950's may now provide a somewhat soupy green appearance, when printed using, for example. Laboratory Aim Densities, which is sold by Eastman Kodak. Laboratory Aim Density is a control film for color control for standardizing reproduc ion.

Another example of color deterioration that tends to occur in color negative films is a fading in which the highlights or white areas appear yellow, while the shadow or dark areas of the image appear blue. This fading characteristic, known as crossover, can prevent an image produced from an original negative from being true to the correct color. One process for restoring color of faded or discolored color photographs (not of negatives) is by chemically treating the photographs ( see U.S. Patent No. 4,717,646). In that process, faded or discolored color photographs are cleaned with a water-free application of anhydrous acetone-free diacetone and coated with a color corrective restoration solution. Exposing certain old photographs or other film media to chemical treatments, however, may not be favored because of the risk of damaging or destroying the media.

Today, typically color negatives are protected by striking an interpositive from the original negative. A duplicate negative can be created from the interpositive. New projection prints created from interpositive and the duplicate negative can be equal in quality to those generated from the original negative. However, negatives that, for example, are over 30 years old may no longer be capable of being restored to their original colors. Even basic enhancement through the interpositive to duplicate negative process typically is substantially ineffective in restoring the original colors. While it may be possible to correct the light areas with the interpositive to duplicate negative process, the process tends to cause the dark areas to become discolored into the blue range. Therefore, there exists a need for restoring color negative film which has faded over time, without the need to expose the original negBee-de£otorehfemrάn$scolor

SUMMARY QT THE DISCLOSURE

In accordance with the embodiments of the present invention, a process is capable of restoring color of a color negative (including but not limited to a copy of an original negative) , including, but not limited to motion picture color negative film (for example, 35mm motion picture color negative film produced by the Eastman Kodak Co.). The process comprises the steps of generating an autopositive from the negative, generating an interpositive from the negative, combining the autopositive with the negative to make a yellow covermatte, and combining the interpositive with the yellow covermatte to make a restored negative.

In another embodiment, the step of combining the autopositive with the negative comprises the steps of creating images of the negative and of the autopositive, aligning these images, overlaying them, correcting towards blue the overlaid images, and recording the overlaid images of the negative and of the autopositive on color positive print stock.

In another embodiment, the step of combining the interpositive with the yellow covermatte comprises the steps of creating images of the interpositive and of the yellow covermatte, aligning these images, overlaying them, correcting towards blue the overlayed images of the interpositive and of the yellow covermatte, and recording the overlayed images on color intermediate film stock.

Another embodiment is a process for making a restored interpositive from a color negative. The process comprises the steps of generating an autopositive from the negative, generating an interpositive from the negative, combining the negative with the autopositive, recording the corrected combination onto the interpositive.

The above discussed and many other features and attendant advantages of the present invention will become better understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram illustrating the steps of generating an autopositive and an interpositive from a faded original negative, in accordance with an embodiment of the present invention.

Fig. 2 is a perspective view showing how the generation of the autopositive and the interpositive in Fig. 1 is achieved with a single apparatus comprising a first projector and a camera. Fig. 3 is a block diagram illustrating the step of generating a yellow covermatte from the original negative and the autopositive, in accordance with an embodiment of the present invention. Fig. 4 is a perspective view showing how the generation of the yellow covermatte in Fig. 3 is achieved with the first projector and the camera of Fig. 2 in addition to a second projector.

Fig. 5 is a block diagram illustrating the step of generating a restored negative from the interpositive and the yellow covermatte, in accordance with an embodiment of the present invention.

Fig. 6 is a perspective view showing how the generation of the restored negative in Fig. 5 is achieved with the same set-up as in Fig. 4.

Fig. 7 is a perspective view further showing a process according to an embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is the best presently contemplated mode of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. The scope of the invention is best defined by the appended claims. In the figures discussed below, the same or equivalent items shown in the figures are identified by the same reference numbers.

Fig. 1 illustrates in block diagram format the first steps in a preferred embodiment of a process for restoring color of motion picture color negative film, which has faded over time. Per the arrows in Fig. 1, a frame containing an original negative 10 is used to generate a frame containing an autopositive 12 and a frame containing an interpositive 14. Fig. 2 illustrates, in more detail, a process of making both the autopositive 12 and the interpositive 14 with the same apparatus. The apparatus shown in Fig. 2 includes a first projector 16 having a feed reel 18, a take-up 20 reel, and a lens 22. A light source 24 provides light for the operation of the first projector 16. An original 35mm motion picture color negative film 26 requiring color restoration is placed onto the feed reel 18 of the first projector 16. Arrows 28 indicate the direction in which the feed and take-up reels 18 and 20 are rotated during the generation of autopositives and interpositives for transfer of the original film 26 from the feed reel 18 to the take-up reel 20. The original color negative film 26 comprises an original negative 10, such as that of Fig. 1.

Fig. 2 further shows a camera 30, which has a raw stock reel 32 and a take-up reel 34. As indicated by the dashed line in Fig. 2, the camera 30 is aligned with the first projector 16. To produce autopositive film which contains frames of autopositives, including the autopositive 12, the raw stock reel 32 of the camera 30 is loaded with raw film stock 36. The raw film stock 36 may be any suitable film stock including, but not limited to, stock produced by the Eastman Kodak Company under the trademarks and/or tradenames "5360" and "Direct MP Stock." Arrows 38 indicate the direction in which the raw stock 32 and the take-up reel 34 of the camera 30 are being rotated during the generation of autopositives and interpositives. The speed of transfer of the raw film stock 36 from the raw stock reel 32 to the take-up reel 34 is synchronized with the transfer of the original negative film 26 from the feed reel 18 to the take- up reel 20. This permits projecting images of the original negative, including the original negative 10, frame by frame through the lens 22 onto the raw film stock 36 inside the camera 30 at location 40. From this raw stock, the camera 30 produces autopositive film, including the autopositive 12 of the original negative 10. As illustrated in Fig. 2, once the autopositive 12 has been generated, it is transferred by virtue of the reel rotation per arrows 38 away from the raw stock reel 32 to the take-up reel 34.

Preferably, the autopositive film, which is produced from the original film, is an ultra fine grain, high resolving power film stock. The autopositive increases the contrast in the step discussed below in the context of Fig. 3. Once all of the frames of the original film 26 have resulted in an autopositive, without changing the apparatus, the raw film stock 36 for making the autopositive film is replaced with another raw film stock 36, this time intermediate film stock. Thereafter, the process described above for producing the autopositive film is repeated. The result is interpositive film made from the intermediate film stock. Any suitable intermediate film stock may be used including, but not limited to, intermediate film stock produced by Eastman Kodak Company under the trademarks and/or tradenames "5244" and "Eastman Color Intermediate." Preferably, the generation of the interpositive 14 is a standard film process timed to a standard Laboratory Aim Density.

Fig. 3 illustrates the next step. The step comprises combining (represented by the addition symbol 42) the original negative 10 with the autopositive 12 to produce (represented by the equality symbol 44) a yellow covermatte 46 preferably on color positive print stock 58. The combining step is performed optically, preferably as discussed below. The yellow covermatte 46 contains information lost from the faded original negative 10.

Fig. 4 illustrates in more detail a preferred embodiment of the step of combining the original negative and the autopositive to produce the yellow covermatte 46. Fig. 4 illustrates combining the original film 26 containing the original negative 10 with autopositive film 56 containing the autopositive 12 using separate heads on a double headed optical printer. The double headed optical printer is illustrated by the first projector 16, a second projector 48, and the camera 30. The second projector comprises a feed reel 50, a take-up reel 52, and a lens 54. As in Fig. 2, arrows 28 indicate the turning directions of the reels 18, 20, 50, and 52 of the first and second projectors 16 and 48. Arrows 38 indicate the turning directions of the reels 32 and 34 of the camera 30. As indicated in Fig. 4 by the dashed line, the lens 54 of the second projector 48 is in line with the lens 22 of the first projector 16, which is in line with the camera 30.

In Fig. 4, the original color negative film 26 containing the original negative 10 is placed into the first projector 16 onto the feed reel 18. The autopositive film 56 containing the autopositive 12 is placed onto the feed reel 50 of the second projector 48. The camera 30 is loaded with color positive print stock 58. Any suitable color positive print stock may be used including, but not limited to, color positive print stock produced by Eastman Kodak Company under the trademarks and/or tradenames "5386" and "Eastman Color Print," color positive print stock produced by Agfa Gevaert NV under the trademark and/or tradename "CP-1" or by Fuji Corporation under the trademark and/or tradename "8213." The rate of transfer of the autopositive film 56 from the feed reel 50 to the take-up reel 52 of the second projector 48 is synchronized with the rates of transfer of the original film 26 and of the color positive print stock 58 to their respective take-up reels 20 and 34 of the first projector 16 and the camera 30, respectively, as described in the context of Fig. 2. The original negative 10 and the autopositive 12 are aligned with each other by aligning, as shown in Fig. 4, the second projector 48 with the first projector 16. The alignment is such that an image projected by the second projector 48 would overlay with the same orientation the same image, if a copy of that image were positioned in place of the original negative 10 in the first projector 16.

Once the autopositive 12 is properly positioned, its image is projected using light from the light source 24 through the lens 54 of the second projector 48 onto the original negative 10 in the first projector 16. Then, the image of the optical combination of the original negative 10 and of the autopositive 12 is projected through the lens 22 of the first projector 16. In addition, that combination also is preferably filtered with a blue filter (not shown) . The blue filtered combination of the original negative 10 and the autopositive 12 is photographed by the camera 30 onto the color positive print stock 58 to produce 44 the yellow covermatte 46.

Fig. 5 illustrates the next steps of this embodiment. The interpositive 14 is optically combined (represented by the addition symbol 62) with the yellow covermatte 46 to produce 64 a restored negative 66. Fig. 6 illustrates in more detail the process of Fig. 5. The process in Fig. 6 uses the same apparatus, as in Fig. 4, except that different stock is loaded onto the feed reels 18 and 50 of the first and second projectors 16 and 48, respectively, and onto the raw stock reel 32 of the camera 30.

Interpositive film 68 containing the interpositive 14 is loaded onto the feed reel 18 of the first projector 16. Color positive print stock 69 containing the yellow covermatte 46 is placed onto the feed reel 50 of the second projector 48. Color intermediate film stock 70 (such as discussed above with respect to the production of the interpositive film) is placed onto the raw stock reel 32 of the camera 30. As discussed in the context of Fig. 4, the arrows 28 and 38 together indicate the direction of rotation of all of the reels. As was done with the original negative and the autopositive as discussed above, the image of the yellow covermatte 46 in the second projector 48 is overlaid by projection onto the interpositive 14. The optical combination of the images of the yellow covermatte 46 and of the interpositive 14, as produced by the first projector 16, is preferably filtered with a slightly blue filter for correcting yellow highlights. Further, this optical combination is projected onto the camera 30 at Docation 32, where it is then photographed onto the color intermediate film stock 70 in the camera 30 resulting in the restored negative 66.

The process of combining the interpositive with the yellow covermatte also may be used to create three black and white film images preferably with red, green, and blue filtered light to create YCS ( ) negatives for archiving. Preferably, the black and white film images are generated with a double headed optical printer, as illustrated in Fig. 6 with the yellow covermatte 46 and the interpositive 14 placed onto projectors 48 and 16, respectively, as in Fig. 6. A first black and white film stock is placed onto a raw stock reel 32 of a camera 30. Although the sequence can be varied, on a first pass, the light from a light source 24 preferably is filtered with a red filter to generate a red filtered black and white archive negative from the first black and white film stock. The process is repeated with a green filter (replacing the red one) to generate a green filtered archive negative on a second black and white film stock (which replaced the first one) . The process is repeated a third time with a blue filter (replacing the green one) to generate a blue filtered archive negative on a third black and white film stock (which replaced the second one) . The first, second, and third black and white archive negatives can be combined to recreate a color restored negative. Since the archive negatives are in black and white, they are likely to last longer than a color restored negative generated at about the same time. The black and white archive negatives can be generated in addition to or in place of a restored negative. The processes described above may be used on a variety of color negatives, not just motion picture negatives, such as 35mm motion picture negatives. Indeed the processes could be used on individual copies of original color negatives. However, the synchronized projecting/recording steps using the apparatuses shown in Fig.'s 2, 4, and 6 are especially efficient with respect to practicing embodiments of the inventive process with motion picture film. But the process steps of Fig.'s 1, 3, and 5 may be practiced with other components and in other apparatuses than those shown in Fig.'s 2, 4, and 6.

In another embodiment, the steps of combining the original negative 10 with the autopositive 12 or combining the interpositive 14 with the yellow covermatte 46 may be accomplished by other suitable means including, but not limited to, a bipac arrangement in which a single head optical printer is employed instead of separate heads on a double headed optical printer, as illustrated in Fig. *s 4 and 6. With a bipac arrangement, a single projector has two pairs of feed and take-up reels with synchronized rates of transfer of the stock from the feed reels to the take-up reels. To illustrate, in the step of combining the original negative 10 with the autopositive 12, one pair of reels is for the original film 26, and one for the autopositive film 56 containing the autopositive 12. One possible disadvantage of bipac is that overlaying the original negative 10 with the autopositive 12 may be more difficult in regard to alignment of the images, than when using separate heads.

In another embodiment, the step in Fig. 3 of combining 42 the original negative 10 with the autopositive 12 to produce 44 the yellow covermatte 46 comprises the step of placing the original film 26 into the second projector 48 in Fig. 4 instead of placing it into the first projector 16. Although, better results may be achieved by keeping the original film 26 in the first projector 16. By placing the original film 26 into the projector closest to the camera 30, light from the image from the original negative 10 has to go through a single lens 22 instead of through two lenses 54 and 22, resulting in a sharper original negative 10 image projected onto color positive print stock 58. In another embodiment, the intermediate film stock 68 containing the interpositive 14 is loaded into the second projector 48 and the color positive print stock 58 containing the yellow covermatte 46 is placed into the first projector 18 in Fig. 6. In another embodiment, the original negative 10 and the autopositive 12 are filtered with a series of blue correction filters, such as are sold under the trademarks and/or tradenames "47", "98", and "CC Blue". In another embodiment, the images from the first and second projectors 16 and 48 are filtered with a blue filter before (instead of after) they are optically combined. In another embodiment, the images from the first and second projectors 16 and 48 are produced with light already filtered with a blue filter. Another embodiment produces a restored interpositive, which is different than the interpositive in the above embodiments. A restored interpositive can be used to make a restored negative by generating an interpositive as in the above embodiments. (The restored interpositive can also be used for transfer to a video format.) To make the restored interpositive, an autopositive is made from the original negative as discussed above. However, this autopositive is made denser and with more contrast than the autopositive in Figs. 1 and 3. An interpositive is generated from the original negative preferably using Laboratory Aim Density standard. Thereafter, the original negative is optically combined with the autopositive preferably with blue filtered light and recorded onto the interpositive located inside a camera 30 to generate the restored interpositive (preferably in a bipac arrangement or in an arrangement with separate heads on a double headed optical printer, as discussed above with respect to Fig.'s 4 and 6).

Fig. 7 further illustrates an embodiment, wherein according to the first two steps of the color restoration process, the original negative 10 is positioned in one of the projectors (preferably projector 80) and photographed by the camera 82. The camera makes an interpositive and an autopositive from the original negative. In the next step; the autopositive is positioned in one projector (preferably projector 84) and the original negative 10 is positioned in the other projector (preferably projector 80) . Which projector each element is put into is not important but preferably the original negative is in the projector closest to the camera for best image detail. With the autopositive and original negative in line with each other, the camera makes the yellow covermatte (or mask) onto color print film. In the final step, the interpositive is positioned in one projector (preferably projector 80) and the yellow covermatte (or mask) is positioned in the other projector (preferably projector 84) . These elements are photographed onto color internegative stock. Having thus described exemplary embodiments of the present invention, it should be understood by those skilled in the art that the above disclosures are exemplary only and that various other alternatives, adaptations and modifications may be made within the scope of the present invention. The presently disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

Claims

WHAT IS CLAIMED IS:

1. A process for restoring color of a negative, the process comprising the steps of: generating an autopositive from the negative; generating an interpositive from the negative; combining the autopositive with the negative to make a yellow covermatte; combining the interpositive with the yellow covermatte to make a restored negative.

2. A process as recited in claim 1, wherein the step of combining the autopositive with the negative comprises the steps of: creating images of the negative and of the autopositive; aligning the image of the negative with the image of the autopositive; overlaying the images of the negative and of the autopositive; correcting towards blue the overlaid images of the negative and of the autopositive; recording the overlaid images of the negative and of the autopositive on color positive print stock.

3. A process as recited in claim 2, wherein the step of correcting towards blue comprises the step of correcting towards blue the images of the negative and of the autopositive.

4. A process as recited in claim 2, wherein the step of correcting towards blue comprises the step of passing light through a blue filter, the light to be used for creating the images of the negative and of the autopositive.

5. A process as recited in claim 2, wherein the step of correcting towards blue comprises the step of passing light from the images of the negative and of the autopositive through a blue filter.

6. A process as recited in claim 1, wherein the step of combining the negative with the autopositive comprises the step of combining their images in separate heads on a double headed optical printer.

7. A process as recited in claim 6, wherein the step of combining the images in separate heads on a double headed optical printer comprises the step of positioning the negative between the camera and the autopositive.

8. A process as recited in claim 1, wherein the step of combining the image of the negative with the image of the autopositive comprises the step of combining the images as bipac in a single head optical printer.

9. A process as recited in claim 2, wherein the step of recording the overlayed images of the negative and of the autopositive on color positive print stock comprises the step of recording with a camera the overlayed images on color positive print stock.

10. A process as recited in claim 1, wherein the step of combining the interpositive with the yellow covermatte comprises the steps of: creating images of the interpositive and of the yellow covermatte; aligning the image of the interpositive with the image of the yellow covermatte; overlaying the images of the interpositive and of the yellow covermatte; correcting towards blue the overlayed images of the interpositive and of the yellow covermatte; recording the overlayed images of the interpositive and of the yellow covermatte on color intermediate film stock.

11. A process as recited in claim 10, wherein the step of correcting towards blue comprises the step of correcting towards blue the images of the interpositive and of the yellow covermatte.

12. A process as recited in claim 10, wherein the step of correcting towards blue comprises the step of passing light through a blue filter, the light to be used for creating the images of the interpositive and of the yellow covermatte.

13. A process as recited in claim 10, wherein the step of correcting towards blue comprises the step of passing light from the images of the interpositive and of the yellow covermatte through a blue filter.

14. A process as recited in claim 10, wherein the step of correcting towards blue comprises the step of correcting slightly towards blue.

15. A process as recited in claim 10, wherein the step of combining the interpositive with the yellow covermatte comprises the step of combining their images in separate heads on a double headed optical printer.

16. A process as recited in claim 15, wherein the step of combining the images in separate heads on a double headed optical printer comprises the step of positioning the interpositive between the camera and the yellow covermatte.

17. A process as recited in claim 10, wherein the step of combining the image of the interpositive with the image of the yellow covermatte comprises the step of combining the images as bipac in a single head optical printer.

18. A process as recited in claim 10, wherein the step of recording the overlayed images of the interpositive and of the yellow covermatte on color intermediate film stock comprises the step of recording with a camera the overlayed images on color intermediate film stock.

19. A process as recited in claim 1, wherein the step of generating an autopositive comprises the step of using a projector to project the negative onto raw film stock.

20. A process as recited in claim 1, wherein the step of generating an interpositive comprises the step of using a projector to project the negative onto intermediate film stock.

21. A process as recited in claim 1, wherein the negative comprises motion picture color negative film having frames, further comprising the step of executing for each frame the steps of generating the autopositive and interpositive, and making the yellow covermatte and the restored negative.

22. A process as recited in claim 1, wherein the negative comprises 35mm motion picture color negative film having frames, further comprising the step of executing for each frame the steps of generating the autopositive and interpositive, and making the yellow covermatte and the restored negative.

23. A process for restoring color of a negative, the process comprising the steps of: generating an autopositive from the negative; generating an interpositive from the negative; combining the autopositive with the negative to make a yellow covermatte comprising the steps of: creating images of the negative and of the autopositive; aligning the image of the negative with the image of the autopositive; overlaying the images of the negative and of the autopositive; correcting towards blue the overlaid images of the negative and of the autopositive; recording the overlaid images of the negative and of the autopositive on color positive print stock; combining the interpositive with the yellow covermatte to make a restored negative comprising the steps of: creating images of the interpositive and of the yellow covermatte; aligning the image of the interpositive with the image of the yellow covermatte; overlaying the images of the interpositive and of the yellow covermatte; correcting towards blue the overlayed images of the interpositive and of the yellow covermatte; recording the overlayed images of the interpositive and of the yellow covermatte on color intermediate film stock.

24. A process for making a restored interpositive from a color negative, the process comprising the steps of: generating an autopositive from the negative; generating an interpositive from the negative; combining the negative with the autopositive onto the interpositive.

25. A process as recited in claim 24, wherein the step of generating an autopositive comprises the step of generating a dense autopositive with substantial contrast.

26. A process as recited in claim 24, wherein the step of generating an interpositive from the negative comprises the step of correcting the interpositive towards blue.

27. A process as recited in claim 25, wherein the step of combining the negative with the autopositive comprises the steps of: creating images of the negative and of the autopositive; aligning the images of the negative and of the autopositive with the interpositive; overlaying the images of the negative and of the autopositive onto the interpositive; correcting towards blue the overlayed images of the negative and of the autopositive.

28. A process as recited in claim 27, wherein the step of generating an interpositive comprises the step of generating the interpositive on Laboratory Aim Density film.

29. A process for archiving a restored negative made from a negative, the process comprising the steps of: generating an autopositive from the negative; generating an interpositive from the negative; combining the autopositive with the negative to make a yellow covermatte; combining the interpositive with the yellow covermatte to make a first black and white negative.

30. A process as recited in claim 29, further comprising the step of combining the interpositive with the yellow covermatte to make a second black and white negative.

31. A process as recited in claim 30, further comprising the step of combining the interpositive with the yellow covermatte to make a third black and white negative.

32. A process as recited in claim 29, wherein the step of combining the interpositive with the yellow covermatte comprises the steps of: creating images of the interpositive and of the yellow covermatte; aligning the image of the interpositive with the image of the yellow covermatte; overlaying a first time the images of the interpositive and of the yellow covermatte; correcting towards red the overlayed images of the interpositive and of the yellow covermatte; recording the overlayed images of the interpositive and of the yellow covermatte on a first black and white film stock.

33. A process as recited in claim 32, further comprising the steps of: overlaying a second time the images of the interpositive and of the yellow covermatte; correcting towards green the overlayed images of the interpositive and of the yellow covermatte; recording the overlayed images of the interpositive and of the yellow covermatte on a second black and white film stock.

34. A process as recited in claim 32, further comprising the steps of: overlaying a third time the images of the interpositive and of the yellow covermatte; correcting towards blue the overlayed images of the interpositive and of the yellow covermatte; recording the overlayed images of the interpositive and of the yellow covermatte on a third black and white film stock.