US1333730A - Method of producing colored photographic images - Google Patents

Description

Patented Mar. 16, 1920.

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APPLICATION FILED APR.3, 1914.

METHOD OF PRODUCING COLORED PHOTOGRAPHIC IMAGES.

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CHARLES RALEIGH AND WILLIAM V. D. KELLEY, 0F BROOKLYN, NEW YORK, ASSIGNORS,

METHOD OF PRODUCING COLORED PHOTOGRAPHIC IMAGES.

Specification of Letters Patent.

Patented Mar. 16, 1920.

Application filed April 3, 1914. Serial No. 829,166.

To all whom it may concern Be it known that we, CHARLES RALEIGH and WILLIAM V. D. KELLEY, citizens of the United States, residing at Brookl n, in the county of Kings and State of ew York, have invented certain new and useful Improvements in Methods for Producing Colored Photographic Images, of which the following is a full, clear, and exact specification.

This invention relates to motion pictures, and has particular reference to means and a method of obtaining reproductions of pictures in natural colors in a much more natural manner than has heretofore been attained. By this invention, it is-possible to produce pictures in natural colors with reduced speed per second, which gives a reduced length of film for exhibiting a given subject. By this invention, color fringing is also very largely if not entirely eliminated.

In one method of roducing motion pictures in colors, it has en proposed to either take or exhibit three pictures, in succession through 00101 screens, each of which passes one of three prim'arycolors, three successive pictures each recording values correspond ing to one only of said three colors. With this method, owing to the widely different color values it is necessary to project all three of these single color images in the space of time usually used to project a single black and white image, that is, at the rate of forty-eight or more pictures per second. This method is disclosed in'United States patent to Lee, et 01., No. 645,477.

In a later method, it has been sought to reduce the speed to about thirty pictures per second by taking or projecting pictures through screens recording two color values instead of three, which color screens have been so selected as to only somewhatv ap proximate natural colors when projected, violetbeing almost absent. This method is disclosed in United States patent to Smith No. 941,960.

In both of the above methods, of which the'latter is at present in use, each section of the color screen is of an independent color, and each image of the film has only a record of one color value.

one into the other.

According to this invention, we reduce the speed to twenty-four pictures per second or therea-bout, by causing each film section to record values corresponding to. two of three primary colors, which color values are derived from a composite screen, so arranged as to pass at least two of the three primary colors for each image. Starting with red, blue and green as the primary or predetermined colors, in one form we divide a movable screen into sections, each of which passes two of these colors. Thus one section will pass red and blue and record corresponding color values on the first picture of the film, the next section of the screen will pass green and red and record correspondin color values on the film, and the next sectlon of the screen will ass blue and green and record corresponding color values on the film. This is for taking, and in projecting it will be understood that positives made from these negatives and each having two color values will be projected through a similar screen. We may accomplish this result either by making each section of the screen of a composite color, or by dividing each-section of the screeen into two predetermined colors and moving it faster so as to expose both colors of each screen section during one picture exposure. By our method, it will be seen that a series of color screens or filters operatin on or in conjunction with three hotograp ic images, causes the cycle of co ors to be completed twice in the space of three photographic images. For comparison, the aforementioned three primary color process completes the color cycle once in three images, and in the incomplete two; color process once in two images, while with our processthe complete color cycle is actually completed in an average of one and one-half images. Color. fringing is reduced by this invention, because each two-color 'ima e embodies a color common to the succee ing image.

At the same time, eye fatigue will be re-, duced, because two of the three nerve color, v

1 00 images will contain in some degree mixtures centers will at all times be excited, since all of colors, so that the successive images blend The photographic exposure in taking also increased, giving Figure 1 represents a section-ofl a taking camera;

Fig. 2 represents a section of film associated with. thethree section composite color screen; a Z i Fig. 3 represents a different color screen, containing the three primary colors and which will be revolved to expose two colors for each film exposure, and r Fig. 4, a still different color screen 1 represents a box containing reels 2, 2 havingfilm 3 wound thereon which is exposed thro-ugh aperture 4 and the usual lens and shutter -mechanism 5. 6 represents a shaft carrying the screen 7, which is revolved in synchronism with the driven shaft 8. The screen 7 shown in Fig. 2 is provided with three sections P, OY and GB, which correspond to the colors approximately purple, orange yellow and, greenblue. That is, each of these screen sections is a composite made up of two of the three primary colors red, blue, green, and thereby each section will pass two of these three colors. With this form. the screen will be revolved so as to expose one section with each section S of the film. The purple screen in Fig. 2 passes and records red, and the yellow screen passes and records red, with the result that redcis recorded in talcing and obtained in projecting. 'The same applies to all the other "colors, it being a matter of mixing the correct amounts of two filter colors in order to get a resultant third color. The correct amount of purple and yellow mixed gives as result, red, because the blue in the purple will cancel the yellow. If we mix yellow and blue-green in proper proportion, we obtain green, because the blue will cancel the yellow. ,If we mix blue green and purple in proper proportion, the green with a little blue will cancel the red and we obtain pure blue. Thus we obtain primary reds, greens and bluesby this process of cancellation in both taking and projecting. In Fig. 3, the screen is composed ofthree colors R, .B, G, corresponding to the primary or predetermined colors red, blue and green. The sections R and B of, the screen will show while sec- 'tion S of the film'isizxposed, the sections G and R will show while the section S, is exposed, and the sections B and G will show while the section S is exposed. In this manner, each film. section will record values corresponding to two co1ors,.it being understood that a film having a panchromatic emulsion will be employed for the negatives. That= is, a film which is rendered sensitive to all colors, and is well known in the art.

A projection of positives with the screen shown in Fig. 3 is accomplished in asimilar manner, that is each image area will be shown through two of the screen sections, one screen section being common to each two succeeding images, the screen making 1 two complete revolutions for each three images, and being of course started in the right relation to the color values recorded by the respective images.

,The apparatus of Fig. 1 represents the manner in which the negatives are taken, from which negatives positives are made and used in any suitable projecting apparatus, except that a color screen is added containing sections of color corresponding to the taking screens and properly synchronized therewith. Thus each picture. will be projected through a screen passing two colors, one of which colors appears on two adjoining images, so that as before stated the color cycle is completed in the space of one and one-half images, or twice in three images. It will be seen that by the method of this invention, wherein two color values are combined in each image, the mean intensity of the light for each image is substantially constant. That is, the total light does not materially vary in successive images, so that they all receive practically the same degree of exposure. This result is due to the fact that each exposure is made with two light waves, that for one color beingof relatively short, and that for the other color, being of relatively long wave length. When combined in each image, the mean or resultant wave lengths (Which determine the intensity of the image) do not substantially vary to such an extentas to require different treatment in developing, printing or projecting for individual images. This is not only advantageous in obtaining the images, but is equally advantageous in developing the negatives, making the positives, and projecting them.

The invention can also be carried out in connection with a two color composite screen, as shown in Fig. 4. In this form,

one sector GB is composed of green and blue, and the other sector OR of orange-red. The screen, is revolved so that two-thirds of the total composite color area shows for each image. This gives all of the red, and part of the green on image S, then equal exposures of the next image S to red and green, and on the third image S of the series, all the green and part of the red. During each exposure, approximately 240 of colors are shown by the screen on each. The first cycle gives 180 of red, and 60 of green, the second cycle 120 of both. red and green, and the third cycle 180 of green and 60 of red. These two composite colors will blue-green condition.

I a three color screen in result, as will be seen blue. That is, the three successive images S,

' S,'S will have color values corresponding generally to these three composite colors. The screen shown in Fig. 4:, is'preferably used for projecting. The screen filters are such that practically all of the spectrum is covered viz :blue-green for one half, orange-red for the other half. Three mnditions exist: (1) At one period there are equal areas of red and green-blue on one image giving a yellow condition, then (2) a large section of red and a small section of green-blue the red therefore predominating, giving the purple condition, then (3) a large section of green-blue and a small section of red, the green predominating giving the This is nevertheless upon consideration. A properly exposed film taken with our process, having good color value, will give satisfactory results when projected, even though the colors of the projecting screen only approximate the colors of the taking screen. That is, we may project through any ofthe screens, shown in Figs. 2, 3 or i. The great value of using the screen shown in Fig. l in projecting is due to the difficulty of using a blueviolet color. It is difiicult, in practice, to get sufli'cient light through this B-V section to bring its intensity up to the intensity of the red; and green sections of a three section'showing screen. On the other hand it is quite? simple to get the same intensity of light through a shutter composed of redin one section and green-blue in the other.

Spinning such a screen, as we have described herein actually gives three color conditions.

This form is especially advantageous with electric are light taking or projections, which contains a preponderance of violet or blue, because the excess of blue can be readilycompensated for to produce the same balance as exists in natural light. Thus if 180 of the screen is orange-red, and the other 180 blue-green, and the screen be revolved at proper speed, image S will receive 180 of red and of blue-green, image S will receive 120 each of red and blue-green, and image S will receive 180 of bluegreen and 60 of red. In each cycle of three pictures, therefore, there will be a correction for the excess blue in the projecting arc light. Thus the connection canbe made either in taking, or in projecting as may be more convenient. The same principle also applies in taking by are light.

It will be understood that by a composite screen, we refer either to a screen as shown in Fig. 2 containing the three composite colors, or the-screens shown in Fig. 3 in which the three primary colors are employed, or that shown in Fig. 4, having two composite colors, but the screen to be so operated as to expose two of the colors to each image, and the same color appearing on two successive images.

It will be seen that the screen is composite to each image'even though its individual sections are composed-of single colors, the composite effect being obtained by revolving the sections of the screen asynchronously with respect to each image.

Where we use the termfilm in this specification, it will be understood that we refer to any transparent support for sensitized photo aphic emulsion, and intend thereby to inc ude fiexible'or stifi plates, or continuous rolls of any known character.

It will be further understood that the invention is not restricted to the employment of a single width film with successive images, as our method of simultaneously obtaining records of two colors on each image and of projecting them to reproduce the natural colors is applicable to various other forms of film.

lVhere we speak of composite colors as purple, we mean a color that will pass practically only thered and blue when viewed in the spectroscope; of yellow, a color that passes red and green; of blue, a color pass ing blue, violet and green;

Having thus described our invention, we declare that what we claim'as new and desire to secure by Letters Patent, is:--

In motion picture recording, the method which consist in recording on successive panchromatic image areas red-blue bluegreen, and green-red color values through a screen composed of red, blue and green sections constituting white light, whereby each area records white light'minus a constituent.

In testimony whereof weafix our signatures, in presence of two witnesses.

' Witnesses: K. G. LE Ann, J. D. ConNoLLY, Jr.

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