US2520842A - Multicolor cinematography method - Google Patents

Description

1950 P. JUlLLET 2,520,842

MULTICOLOR CINEMATOGRAPHY METHOD Filed Oct. 15, 1947 23" 1}: QM uiggjl role. I

B MM W Patented Aug. 29, 1950 MULTICOLOR CINEMATOGRAPHY METHOD Pierre Juillet, Albon, France Application October 13,1947, Serial No. 779,499 In France October 23, 1946 6 Claims. (01. sir-16.4)

My invention relates to cinematography in natural colours and more particularly to the methods wherein the different hues of the image seen by the observer result from the addition of a number of primary colours (generally three, sometimes only two).

In these methods there is projected on the cinematographic screen a number of successive images taken through monochromatic filters, the said images being coloured by passage of the projected rays through coloured filtering screens identical to the said filters. These successive images are seen by the observer as a single image in natural colours.

When the images of a colour cycle (which will be supposed hereinafter to comprise three primary colours) are taken simultaneously, the film speed through the projecting apparatus is to be multiplied by three with respect to the usual speed of the white-and-black cinematography if the same impression of continuity in the motion of objects is to be preserved. This leads in practice to the projection of 72 images per second, which is too much for most existing apparatus adapted for the standard speed of 24 images per second.

When the three images of a cycle are taken successively, the film speed has not to be increased and may remain at the usual standard of 24 images per second, but the successive images are no more identical and they do not combine correctly for objects in motion. The edges of such objects therefore appear as formed of the three primary colours in juxtaposition (as in a rainbow), which is a material drawback. g:

It has also beenproposed to' project simultaneously on the screen the three images of a colour cycle, the said images being exactly superposed. If these images have been taken simultaneously, this method avoids all the above inconveniences, but it requires delicate apparatus and much skill to obtain exact registration of the three elementary images on the screen.

Moreover the known methods require that the three images of acycle should be taken exactly from the same point, since these three images are to be exactly identical apart from the colour. When such is not the case, the objects taken at short distance give rise to images which do not full register on the screen which again produces coloured edges;

A first object of my invention is to avoid colcured edges on moving objects or on objects at short distance from the camera.

My invention relates to a method wherein there are projected at the same time on the screen two elementary images in juxtoposition, these images being of diiferent colour and the colour of each image following the selected cycle of primary colsuccessive pairs of images the observer thus sees a succession of images and perceives a single moving image in natural colours finally resulting from the addition of all the elementary colours.

In the usual casev of three primary colours, if I 2, 3, designate the primary colours, the successive pairs of imagesmay be represented by l2, 23, 3--|, l-2 and so on, or l-3, 2-4, 3-2 and so on.

Each elementary image thus passes through the whole cycle of colours and would by itself ensure the perception of natural colours. But owing to the juxtaposition of two images at the same time on the screen, the speed of combination of ele' mentary colours is much higher than in the known processes. In the usual case of three elementary colours and with a film speed of 24 images per second, it takes 2%.- of a second to have a full cycle of images. In my method a pair of images such as l--3 will appear on the screen during substantially-2% of a second. The duration of a luminous perception on the human eye being at least of a second, the observer will still see the said pair during 2%= of a second, that is during one half of the time of projection of the next pair .formed of images 2-l. Thus the combination of primary'colours will be perfected within 1% of a second against in the known methods. The drawback of coloured edges will be reduced to a, minimum since moreover two elementary images will be seen simultaneously.

According to a characteristic'feature of my invention the combination of colours is much improved by projecting each elementary image successively in two colours which give by additive combination the primary colour in which this image has been taken in the camera, the second one of these two colours being the first one used for the projection of the same image in the next cording to my invention in a three-001011;;-system,

Figs. 2 and 3 diagrammatically show, in eleva tion and in plan view two devicesfor'the-pmi tion of such films.

Fig. 4 is a front view of a coloured filli ri disc. used for taking views ina three-colour system.

Fig. 5,is.a.fr ont view of. an adjustable. circular screen for the projection of a threeecolour, film.

Fig. 6 is alongitudinalsection thereof.

Eig. .7. is a .diagrammatical .elevationillustrating a. device for, the observation. of. the; projections.

Eig, 8'; is. the. corresponding; plan view.

Eig., 9. a. diagrammatical illustration, of, a. cameraiorv the. obtentionorafilm of the. kind of, Fig. l.

'IihefilmcrFig. lcarries. a succession of. pairs oi; elementary images. taken through three difierent lour fil rsacc rdin h hreercolo r' ystem... he e. ima es e. pos d. ne. above. theother in achpa n. The u cs ivepairsha bee ie encecl'. 1.1;. II; and so h e h ima es. ar referen ed 1. 10. 13 according to the primary colour. to which they correspond. It will beobservedithat'each image of the pairs, f or instance the upper one, is successively 3,1,2. and so on in the successive pairs, While the lower one is l, 2, 3. the successive pairs being -3; 2*l and 3-2; It will be observed that the colour cycle. comprises three pairs and six images.

images.

The images, taken throughappropriate monochromaticfiltersjn a manner perse well known, mightbecoloured on the film itself; butthis would involve considerable difficulties and itis preferable to use filtering screens in the pro ject-ing apparatus, these projection screens carrying the same colours as-those used in combination with the camera.

Fig. 2 illustratessuch' an arrangement comprising a rotary disc ill disposed between the film H to be projected and the projecting lens i2. This disc-is providedwith transparent coloured areas forming filtering; screens for; the rays emanating from the-film-. It comprises acoloured portion for-each film imageand must bedisposed close to the-film-to avoid that rays from afilmimage may-pass through the-filteringarea corresponding tothe other image.- There: is obtained on the projection screen a pairof. coloured images disposed one above the other.

Fig; 3- illustrates a modified arrangement comprising twoprojecting lenses l2 and 12" each adapted to receive selectively therays from onefilm image. Thebundle of rays from each image is reflected twice by a double prism I3 'or I3", whereby lenses l2 and i2 may be disposed in rather spaced relation. In such a case-the filtering disc- Iii may beplaced in front of the lenses as illustrated;

The filtering disc-should of course rotate in synchronism with the film advancing gear and it must be provided with a number of pairs of coloured areas corresponding to a whole number of colour cycles.

Fig. 4 illustrates a filtering disc for a threecolour system, its coloured areas corresponding to the film images of Fig. 1. It comprises three sector-shaped. pairs of. coloured. areas, which havebeenreferenced after the-colours to which they correspond.

It will be evident that the disc of Fig. 4 eilects one rotation for three film advancing motions. In other words the disc eilects one rotation for each; whole cycle of the image pairs on the film. It would of course be possible to devise discs eilecting one rotation for any whole numberofsuch cycles, as will be apparent for any oneskilled in the art.

In accordance with my invention, in a threecolounsystem each image is projected in two successiye. colours. difierent' from the primary colour to which, it corresponds, but so selected that. their. combination reproduces this primary colour. Supposing for instance thattheprimary colours are, as usually, red, yellow and blue, instead of projecting the image corresponding to the red through. a red filtering screen during the whole projection period or /24 of a second, it is successively projected through an orange filtering screenduring /48 of a second and through a .violetscreen during another- 74a of asecond. The observerperceives an image coloured in red. In the same manner the image corresponding to the yellow will be projected through orange and green screens, whilethe image corresponding tothe blue will be projected through green and violetscreens.

It willberemarked that there is thus obtained another regular cycle of three colours: Orange, green and violet. In addition each image in the successive pairsis projected at the beginning of -a projectionperiod in the same colouras: at" the end of: the preceding period; For instance the upperimage will be projected as' follows: first'period, violet: and; orange; second period orange and green; third period, green and violet; and so on.. Inother: words the change of colour is effected. between; the. successive changes: oflpair-of' images. This leads to. a: remarkable feeling: of continuity for the observer.

Figs. 5 and Gillustrate a gearing" adapted for such: a method. Thecoloured areas I, 2' and 3 cover practically the-wholecircular development of the disc- Waszagainst the disc ofiFig. 4. The disc is: driven .by means .of:a. planetaryrmechanism embodying-a sun wheel l l keyedeon the actuating shaft- [5: rotating: insynchronism with the film advancing gearing, planet gears 16 carried by a supportl fl, andian internally. toothed crown wheel lil mechanicallyin one with disc' I0. Support IT iskeyed ona shaft [9' frictionally locked by a. spring 20, but adjustable in angular position by means of a knob 2|.

This disc operates in combination with the usual shutter of' the projection apparatus and it is so disposed that during a projection period the rays from the film images pass successively through two successive pairs of coloured areas such as. I3 and 2|, for instance. By operating knob 2| it is possible to adjust at will the timing'ofthe-passage from one pair of coloured areas to the next one and to correct any defect which might appear on the projection screen in thehues' of the pictures;

It will be apparent that any gearing with three members in mutual connection (mechanisms with three degrees of freedom) may be substituted for the planetary gearing described. For instance there might be employed the wellknown differential gearing used in automobiles.

Figs. 7 and 8 diagrammatically show how the images projected on the projection screen may be observed, There is disposed in front of each eye a double reflecting device 22 or 22" enabling the eye to see only one image and these two devices are adjusted until the two virtual images perceived by the observer are in perfect registration forming a single image in natural colours.

Fig. 9 illustrates an arrangement for obtaining the negative film by means of which positive films such as those of Fig. 1 may in turn be obtained. This arrangement comprises two lenses 23' and 23 disposed one above the other, two double reflecting prisms 24' and 24", and a filter disc in rotating in front of lenses 23 and 23". This arrangement is quite similar to the projectin device of Fig. 3.

In my improved method there exists a certain difference between the images of a pair owing to the distance apart of the two lenses 23' and 23" (difference in space or space parallaxis). But this defect does not exist between the successive upper (or lower) images since they are taken with one and the same lens, There also exists a certain difference between the successive upper (or lower) images since they correspond to successive moments, that is to successive positions of moving objects (difference in time or time parallaxis). But this defect does not exist between the two images of each pair which are taken simultaneously.

It will thus be understood that the importance oi. the above defects is quite reduced. Coloured edges are practically unapparent.

My invention is of particular advantage in combination with stereoscopic cinematography employing elementary images in juxtaposition on the projection screen, since it then only requires the use of filter discs without any modification of the apparatus.

It will moreover be understood that the above description has been given merely by way of example and that it does not limit my invention as defined by the appending claims. The images have been shown as disposed one above the other,

but they could also be arranged side by side.

I claim:

1. A method for cinematography in natural colors which consists in recording on a cinematographic film a succession of monochromatic images of the object according to a first cycle of three primary colors; and in projecting said images on a screen in proper succession while imparting to each in succession two colors of a second cycle of three primary colors, the said two colors being such that they give by additive combination the primary color in which the image has been recorded, and the last one of these two colors being the same as the first one imparted to the next image occupyin the same place on the projection screen.

2. In a method as claimed in claim 1, the step of adjusting the respective durations of projection of each image in each primary color of said second cycle.

3. A method for cinematography in natural colors which consists first in recording on a cinematographic film successive pairs of juxtaposed monochromatic images of the object, the two images of each pair being taken simultaneously in difierent primary colors and each image in the successive pairs passing successively through a first cycle of three primary colors; second in projecting the said pairs of images in succession on a projection screen, the images of each pair being simultaneously projected on the screen in close but spaced relation; third in imparting in succession to each projected image two colors of a second cycle of three primary colors, the said two colors being such that they give by additive combination the primary color in which the image has been recorded, and the last one of these two colors being the same as the first one imparted to the next image occupying the same place on the projection screen.

4. In a method as claimed in claim 3, the step of adjusting the respective durations of projection of each image in each primary color of said second cycle.

5. In a method for cinematography in natural colors by successive projection of monochromatic images corresponding to a predetermined cycle of three primarycolors, the step of projecting each image through two successive coloured filters the colors of which give by additive combination the primary color of said predetermined cycle of colors to which this image corresponds, the second used of said coloured filters being the same as the first used for projection of the next image occupying the same place on the projection screen.

6. In a method as claimed in claim 5, the step of adjusting the respective durations of projection of each image through each of said coloured filters.

PIERRE JUILLE'I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,209,420 Featherstone Dec. 19, 1916 1,261,800 Evans Apr. 9, 1918 1,514,543 Lane et al Nov. 4, 1924 1,579,024 OGrady Mar. 30, 1926 1,816,083 Hnatek July 28, 1931 FOREIGN PATENTS Number Country Date 195,630 Great Britain Dec. 20, 1923 219,957 Great Britain Aug. 13, 1925 319,723 Great Britain Jan. 2, 1929 825,604 France Dec. 16, 1937 478,501 Great Britain Jan. 17, 1938

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