US2270746A - Color photography - Google Patents

Description

Jan. 20, 1942. c. w. wYcKoFF Y coLoR PHOTOGRAPHY Fiied March 13, 19:55;`

2 Sheets- Sheet l Chlor Tf-anspararqy /adr and h/tc l Positive Jan. 2o, 1942.

c. w. wYcKoFF 2,270,746 COLOR PHOTOGRAPHY A Filed March 15, 1939 2 Sheets-Sheet 2 Bch'fg j Support n/ors FIG. 7 the?r Summer-z.l

Patented Jan. 2o,r 1942 Application March 13, 1939, Serial No. 261,468

My invention relates to color phptography and more particularly relates to a novel method and vmeans of producing photographs in natural color onpaper or other opaque support.

In mechanically printing pictures in color upon paper, it has been the practice to employ such methods as the four color halftone method and others. While this method produces very good pictures in natural colors,` it is very expensive and diiiicult to perform and great care must be exercised to obtain registration in printing each of the four copper halftone printing matrices. 'I'he ilnished print upon close inspection is found 9 Claims.

a print in natural color on paper or other opaque sheet;

' to be made up of tiny dots of the three primary colors and black. The human eye is incapable of detecting these tiny dots, assuch, and con-` sequently what is observed is the illusion of a blending of these dots to produce the desired appearance.

I am also aware of a process of photographically printing pictures in color in which the print is not composed of tiny dots as above described, but in which the hues or tones are continuous and the separate colors are superimposed one upon the other. Such a process produces satisfactory prints, but a great deal of expense, time, and precision is indispensable to the production of good prints. l

It is one of 'the objects of the'present invention to' eliminate the disadvantages of the processes heretofore known and to provide a process or method of producing prints on paper in natural colors of superb quality and at low cost.

Another object of my invention resides in provision of a trlfcolor screen filter by the use of Figure 2 is an enlarged plan view of the tricolor filter employed in my process;

Figure 3 is a vertical section showing the color transparency and the tri-color iilter superimposed on a sheet of panchromatic film and which illustrates one of the steps of my process;

Figure 4 is an enlarged plan view of the exposed and developed positive as a result of the preceding step;

Figure 5 isA a section taken on line 5 5 of Figure 4 illustrating the developed positive, and shows the same superimposed upon the colortone controller;

Figure 6 shows in enlarged plan the colortone controller after it has been exposed to light as indicated in Figure 5 and then developed;.

Figure l is an enlarged plan of a lined support;

Figure 8 is a vertical section through the superimposed lined support and colortone controller, and t l Figure 9V is an enlarged plan of the finished plint in natural color made in accordance with my improved process.

The above ilgures are all lined for color in the conventional manner required in such cases, al-

though I have indicated the colors numerals referred to in the drawings.

Other objects and advantages of my invenherein by l tion will become more apparent from the followywhich a singlejcmposite negative. of predetermined pattern may be made.

Agfurther object of my invention is the process*4 of printing photographs in natural colors, in

which only one ngative processed into a positive need be made.: i

A further object 'consistsin producing such a positive transparency which may be used as a negative over and over again as is the case with the familiar negative in black and white photographic printing.

Other objects and advantages of my invention will become more apparent from thefollowing description of an embodiment thereof, reference being made to the accompanying drawings in which-like reference characters are employed to designate like parts throughout the same.

In the drawings- Figure l is a plan view of a portion of a color transparency which it is desired to reproduce as ing description of one embodiment thereof.

By my invention I have found that it is possible to produce photographic prints in natural color at extremely low cost and with a minimum of time and skill.

comes important since it enables amateur photo,

The invention therefore begraphers to produce very satisfactory natural color photographs at low cost and further encourages the commercial production of natural color photographs, which according to methods now used, are very expensive to produce, and are therefore not commercially practicable.

In carrying out my inventionfI have devised a rather simple and inexpensive method and means for producing naturalcolor photographs which includes the vuse of a multi-color screen iilter I of 'predetermined pattern for producing a composite negative which in turn is processed into a positive transparency 2 by the reversal method of developing.

Another element used in my improved process is what I term a color tone controller 3 which consists of a transparent sheet coated with an emulsion including gelatin and an opaque substance, such as, for instance, zinc oxide or talcum powder.

native the controller may comprise a transparent Finally, I employ a support, preferably of heavy white paper 4,`upon which is provided a pattern in any three primary colors, such as blue-green, magenta, and yellow, and in the identical predetermined size and design of the pattern of the lter.

I will now proceed to describe in detail a process in accordance with my invention.

Assuming that one desires to make an enlarged print on paper and in natural colors from a transparent lm such as a frame of a moving picture Kodachrome iilm 5, the subject frame is rst selected and then fixed in the usual manner in an enlarger, and the image properly iocused to the desired degree of enlargement.

For best results, a sheet of supersensitive panchromatic lm 6 is then placed upon the enlarging easel emulsion side up after the proper adjustments have been made and after the lights have been turned oi.

According to my invention, and as illustrated in Figure 3, a multi-color separation screen filter l is then placed iiat upon the emulsion side of this film and a piece of clear glass is superimposed over the screen lter to insure good contact of the screen filter with the film.

The multi-color separation lter, which I employ may be described as a sheet of transparent material, such as Celluloid upon which is coated in any predetermined geometric pattern, transparent colors, such as orange-red l, green "B, and blue-violet 9, complementary respectively to the above mentioned primary colors;

In the embodiment shown, the orange element of the filter takes .ne form of parallel lines equally spaced, whereas the green and blue-violet elements are in the form of squares which -B11 inthe spaces between the orange lines.

These orange -lines are so-regulated in width that the width times the length 'of a side adjacent to 4 two alternate green and blue-violet squares equals the area of one of the squares.

The alternating green and blue-Violet squares are equal in area. Therefore, each of the three colors has an equal area.' Furthermore, the density of each of these three colorscan be such that all three may have equal filter factors.L

With this filter in place upon the film as .described above, the exposure is made through the lter, as indicated in Figure 3,. After the proper exposure is made, the filter is removed and the exposed film is then developed, washed, bleached, and re-developed by the usual reversal method to produce a composite color separation positive 2 instead of a composite color separation negative which-Would result in the absence of redevelopment.

This positive is then washed and dried.

In accordance'with this invention I also provide what may be termed a` color tone controller 3. The controller comprises preferably a sheet of Celluloid or similar transparent substance lil coated with a light sensitive nitrate emulsion containing a finely divided white substance H, such as zinc oxide or talcum powder, to render it opaque, and developed in the usual manner as in developing a black and white negative, or

it may be coated with a gelatin emulsion containing a iinely divided -white substance to render it opaque. In the latter case the coating may be rendered light sensitive by immersion inv a bichromate bath and then dried. As an altersheet I0 coated with a light sensitive emulsion .whose image may be rendered White by chemical reaction in development.

In further carrying out the process, the color separation positive element is placed in contact with the support side of the controller sheet, and a sheet of clear glass may be superimposed over these elements to insure absolute contact therebetween.

With the parts thus in place, as shown in Figure 5, an exposure is made through the color separation positive 2 and upon the light sensitive surface of the controller element. When the proper exposure is made, the gelatin coated controller element is then immersed in a bath of relatively hot Water, that is, at a temperature of about to 120 F., for about ve minutes..

The hot water dissolves the unexposed portions of the gelatin containing the iinely divided white powder, but leaves a hardened opaque white negative image in the direct proportion to the amount of light reaching the exposed portions of the controller nlm.

After immersion in the hot water, the controller may be immersed for a brief time in cooler water for xation, and then dried.'

When a nitrate coated controller is employed, it is developed in the same manner as'is the usual black and white negative.

The next step in my improved process consists in 'producing the image in natural color upon a specially prepared support i2. This support primarily may consist of a sheet of paper, such as is used in producing ordinary black and white photographs, and on which is printed a geometric pattern of colors complementary to the respective primary colors of the lter I and which correspond exactly in size and shape with the color pattern and elements of the separation screen lter. It will be recalled that the respective colors used in the filter are orangered; green; and blue-violet, but the colors printed on the support are the complements thereoi,

.. namely; blue-green i3; magenta iti; and yellow i5 respectively.

The geometric pattern of these primary colors, blue-green; magenta; and yellow is printed upon thewhite paper support, and this surface may be coated with a layer of transparent gelatin, so as to provide means whereby the controller may ce fixed to the support.

In carrying out this step in my process, it may be explained that the color tone controller is laid emulsion side down upon the coated surface of the support. The controller element is shifted about upon the surface of the support until the image seems to have the proper color balance or hues. y

The controller element which has been exposed as described above, contains the image to be reproduced in color on the support. The

true color values on the support are determined by the densities of the undissolved surface of the controller when the controller element is superimposed thereon while the true color bal-` ance is obtained by shifting tlie controller upon convenient means, and a steady even pressure is applied until the print is dry.

When the print is dry, the support of the conytroller element may be stripped oi the print, if desired, although this is not necessary. In any event the photographic print thus produced will be found to be an accurate reproduction'in natural color.

three selected primary colors of blue-green,

magenta, and yellow as described above. l

In either case, the pattern must be such that the blue-green areas or portions coincide exactly in size, shape, and spacing with the orange areas of the filter. Likewise,- the magenta and yellow portions must coincide exactly with the green and blue-violet portions, respectively, of

`the filter.

Ihave found that color prints can easily be made in laccordance with my improved photographic method with high iidelity to color value and tone and that the finished prints possess true natural color reproduction. Furthermore, by my method, one is enabled to produce photographic prints in natural color at very low expense and in a very simple manner.

I have shown the individual color areas in the drawing in greatly enlarged size for purposes of clearness, but in the actual practice of my method or process these areas will be greatly reduced and will be minute in size.

The essential thing to remember is that an opaque white negative image is absolutely necessary in carrying out the above described process since it is the only way in which the whites of the picture can be produced. Furthermore, it might be added thatv it is better to mix the various colors with white rather than black for reasons of brlliancy and clearness.

Various changesv may be made in the details of carrying out my method without departing from 'the spirit of the invention or the scope of the appended claims.

I claim:

l. The process of photographically producing images in natural color upon an opaque support which includes the successive steps of printing an image in natural color uponA a sensitized lm or plate beneath a screen having a geometric pattern composed of minute areas colored in the primary colors, processing said lm or plate after exposure to produce a positive having recorded thereon monochromatic color value areas corresponding to the form of the image, printing said iilm or plate upon a film having a light sensitive emulsion containing a finely divided white substance, developing 'said iilm to remove the unexposed portion oi the emulsion and leave a white negative image, and superimposing said film in a selected position on a support having thereon thefcolors arranged in a geometric pattern identical with the pattern oi the taking screen but in colors complementary thereto, and

2. The process of photographically producing images in natural color upon an opaque support which includes the successive steps of printing an image in natural color upon a sensitized iilm or plate beneath a screen having a geometric pattern composed of minute areas colored ,in the l primary colors, processing said film or, plate after exposure to producepa positive having recorded thereon monochromatic color value 'areas corresponding to the form of the image, printing said film or plate upon a fllm having a light sensitive emulsion containing a iinely divided white substance, developing said film to remove the unexposed portions of the emulsion and leave a white image, and superimposing said iilm in a selected position on a support having `thereon the `colors arranged in a geometric pattern identical with the pattern of the taking screen but in colors complementary thereto, securing said film and support together in registered position.

3. The process of photographically reproducing an image in natural color upon an opaque support which includes the steps of exposing a sensitized transparency beneath a tricolor screen composed of a geometric pattern coloredr in the primary colors to thereby record on the transparency color values, developing the recorded image into a positive, then exposing a nlm' hav-` ing a light sensitive emulsion containing' an opaque white substance through the positive, then developing said iilm into a white negative image by removing the unexposed portions of the emulsion, then superimposing said negative in registered position on a support containing a geometric pattern of the colors identical with the pattern of the selected colors of the taking screen but in colors complementary thereto.

4. 'I'he process of photographically reproducing an image in natural color upon anopaque support which includes the steps of exposing a sensitized transparency, beneath atricolor screen composed of a geometric pattern colored in the primary colors to thereby record on the transparency monochromatic color values, developing the recorded image into a positive, printing through said positive onto a lm, developing into a negative white image then superimposing the white negative in registered position on a support containing a geometric pattern oil the primary colors identical with` the r`pattern of the screen, and then bonding said support and whitey negative together.

5. The process of photographically reproducing an image in natural color`upon an opaque support which includes the steps of exposing a sensitized transparency beneath a tricolor screen composed of a geometric pattern colored in the primary colors to thereby record on the transparency monochromatic color values, developing the recorded image into a positive, exposing said positive onto a'iilm with a white substance incorporated in its emulsion, developing-the recorded image into a white negative image by removing the unexposed portions of the emulsion, then superimposing the white negative in registered position on a support containing a geometric pattern of the colors identical with the pattern of the taking screen but in colors comparency color values, developingl the yrecorded image into a positive, exposing the positive on a sensitized support containing a white substance within its emulsion, developing the recorded image by removing the unexposed portions of the emulsion, then superimposing the developed white image in registered position on a support containing a geometric pattern of the colors identical with the pattern of the taking screen, but in colors complementary thereto, and then bonding said support and White image together.

'7. The process of photographically reproducing an image in natural color upon an opaque support which includes successive steps of exposing a sensitized nlm or plate beneath a tricolor screen composed of a geometric pattern colored in the primary colors to thereby record on said lin or plate monochromatic color value areas, developing the recorded image into a positive, exposing said positive to a lm with an opaque white substance incorporated in its emulsion, developing the film into a White negative image by removing the uneXposed portions of CHARLES W. WYCKOFF.

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