US884254A - Process of photomechanical reproduction of colors and the resultant article. - Google Patents

Description

0. G. ZANDER.

PROCESS OF PHOTOMB AND THE RESULTANT ARTICLE.

2 SHEETS-SHEET l No. 884,254. Q PATENTED APR. 7, 1908.

G. G. ZANDBR.

PROCESS OF PH OTOMEGHANIGAL REPRODUCTION OF COLORS AND THE RESULTANT ARTICLE. APPLIOATION FILED P33. 6, 1905.

2 SHEBTS-SHEET 2.

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UNITED STATES PATENT OFFICE.

. GHARLES GUSTAV ZANDER, OF FINSBURY PARK, LONDON, ENGLAND.

PROCESS OF PHOTOIEECHANICAL REPRODUCTION OF COLORS AND THE RESULTANT ARTICLE.

Specification of Letters Patent.

Application filed February 8, 1905.

Patented April 7, 1908.

Serial No. 244,586.

To all whom it may concern:

Be it known that 1, CHARLES GUSTAV ZAN- DER, a subject of the King of Great Britain, residing at 2 Portland road, Finsbury Park, in the county of London, England, have invented a certain new and useful Process of Photomechanical Reproduction of Colors and the Resultant Article, of which the following is a specification.

- This invention relates to an improvement in the process of hoto-mechanically reproducing colors and t e resultant article, whereby the range of -mixed color which can thereby be reproduced is very considerably extended, the reproduction of homogeneous grays and of dense black or neutral gray is greatly facilitated, and other incidental efects and results are secured. These results are obtained by the practical application of a new and improved color scheme which is ap plicable to every process of photo-mechanical color reproduction, such as ty ographic blockprinting in half-tone, line an the like, photoithograph (either from stone or metal plates) co oty e, photoravure, Woodbury type, and the Ike, and a so-to the reproduct1on, by super-position, of transparencies m color.

The principles underlying the invention are discussed with reference to the accompanying drawings, in which Figure 1 is a comparative diagram of the mixing areas of the improved complementary scheme, and of the ommercial and theoretical three color reproduction schemes. Fi s. 2, 3, 4, and 5,are diagrams illustrating t e overlapping of the color records and showing the relative positions of the reproduction colors and selective color filters according to the improved scheme and their absor tion in the spectrum. Fi 6 shows the resu t of the super osition of t e spectra of Figs. 2, 3, 4, and 5.

he color scheme adopted is based on the assumption that there are four fundamental or mono-chromatic constituent color of a continuous white light spectrum, by mixtures of which in suitable proportions any color in nature can be reproduced. The

hues of these four colors are approximately indicatedby the popular terms:magenta .red, lemon yellow, emerald green, and ultramarine blue. Of these, the three last are found in the spectrum-of white light occupythe positions correspondin' approximatly to the so-call'ed Fraunho er hnes D,

E to b, and about midway between F and. G respectively. The magenta red is not apparent in the continuous spectrum but is or approximates to that color which is known as extra-spectral urple and is obtained (diluted with white) y overlapping the red and violet ends of the spectrum in the well-known manner. It is, in fact, the fundamental or mono-chromatic color which when combined with yellow gives spectrum red, and when combined with blue gives spectrum violet. It will be found that these four fundamental color can be grouped in two pairs of complementary color, .VlZ. red and green, and yellow and blue, so that when the elements of either pair are mechanically mixed, as by printing or staining, they produce black, while the effect of their 0 tical combination is the sensation of white lght.

Although the hues above specified by their popular names ive very satisfactory resu ts, they may e departed from to some extent without detrimentally affecting the results obtained to any great extent, and such departure may be necessary or advisable in certain circumstances, as for example, when it is desired to use more permanent pigments as reproduction color than those which most nearly yield the four fundamental hues described. Thus, one .or more of the following substitutions may be made:

carmine for magenta, sulfur yellow for lemon yellow, peacock green for emerald green, vioet blue for ultramarine. At the same time it is to be noted that the hues selected respectively for the red and een pair and for the yellow and blue pair s ould be as nearly as possible complementary to each other. The allowable variation in the four fundamental colors and the s ectral positwn of the preferred colors are est ex ressed by reference to their wave-lengths. lhus, for the yellow may be used any or all of the hues havin wave-lengths between 6000 (10.7 .m. in.

and 5600 (10.7 m. m.) for green, any or all of the hues having wave-lengths between 5500 (10.7 m. m.) and 5000 (l0.7 m. 111.); for blue, any or all of the hues having wave lengths between 4900 (10.7 m. m.) and 4200 (10.7 m. m.); while the-limits of the red are defined b thecom lementary color of any or all of t e'hues o spectrum green between wave-lengths 5500 (10.7 m. m.)'

ing to wave-lengths 5890 (10.7 m. m. about D line), 5220 (1037 m. In. about E b) and 4580 (10.7 m. m. about F 1} G), together H with the color complementary to that of wave-length 5220 (10.7 m. m.)

The fact that either of the two airs of proposed complementary colors is ali'eady sufficient to produce black or ray, which is impossible with any two co ors at present in use for photo-mechanical color reproduction, these being essentially non-complementary,

enables the reproduction of dense black or' circle re resents a continuous spectrum bent on itsel to overla the red and violet ends so forming the c ornatic or color circle, which will contain in its area all possible hues arising from the mixin of the several spectral colors. The relatlve positions of the Fraunhofer lines and spectrum colors are approximately shownby the letters and names appropriate thereto.

he comparative mixing areas of the fourcolor process of, the resent invention (in which the fundamenta or monochromatic, colors are theoretically identical with the spectral colors indicated at 1, 2, 3, 4, in Fig.1) and of the theoretical or fugitive threecolor process (in which the fundamental, or monorecords or negatives are made comb nation of suitable color-sensitive p 0-.

chromatic colors are theoretically identical with the spectral colors indicated at 4, 5 and 8 in Fig. 1) are respectively shown in Fig. 1 by the s uare 1, 2, 3, 4, and the triangle 4, 5, 8 (whic is of much smaller area) that is to say, the invention greatly increases, theoretically, the range of mixed colors ava ilable, as also the reproduction of the subdued shades and tints, in the same proportion as the area of the s uare is greater than the area of the triang e, for the square and the triangle respectively contain only those hues thatare ossible from the mixing of the spectral co lors indicated at their angular points, while any shades that cannot be imitated b the mixing of said colors willbe' outside t e areas of the respective figures. Practically the increase is greater since the mixing area of the usual three-color process is limited, commercially, to the area of the smaller, or dotted triangle, 5, 6, 7 in Fig. 1, where the radial or shade Prussian h ue colors, with respect to the spectral colors,)are, for the sake of comparison, estimated approximately. l

In carrying the color scheme into practical effect, the requisite photogra hiccolory usm fa positions of the 'madder lake andtographic prllates and selective color filters, each of w 'ch, roughly speaking, should pass all the colors of the spectrum with the exception of the respective reproduction I that there should be overlapping in the green and red records in the region both of the D and of the G lines, and in the yellow and blue records in the region of the lines E and I). These overlappings, the extent of which is discretionary and may be determined empirically, Eproduce corresponding gaps at D, G and to b in the posltives, whereby the production of the yellow, spectrum reen and blue respectivey may be eflecte The overlapping of the color records is illustrated in diagrams 1, 2, 3 and 4 of Fig. 6, and the result in the production of the spectrum color is shown in diagram 5.

J The choice or making of suitable color sensitive photographic plates, color filters, their spectroscopic measurements, correct exposure. and kindred technical mampulations are matters of detail which resent no inherent difficulties to persons Skl led in-the art, and as such form no essential part of the present invention. Similarly the selection of suitable dyes, pigments or ink for the reproduction color is also a matter of experience and 'udgment, and in some cases expediency, ut in any case the limits of color erein described should not be exceeded. I

Having thus described this invention and the best means I know of carrying the same into practical effect,, I claim:

1. A process for the hoto-mechanical re production of colors wliich consists in proucing hotogra hic color records or negatives ta en on our suitable color-sensitive plates or films, each of' a character to be unacted on by a different one of a grou of four fundamental or monochromatic co ors constituting two pairs of complementary colors' and in. em loying said records or production of colors'in which the requisite photographic color records or negatives are taken on four suitablecolor-sensitive piates or films, constituting two pairs of complementary colors (blue and yellow and green and red) which are defined respectively .as any hue of the continuous spectrum of white lig t between wave lengths 4200 and 4900 (10.7 m. m.) the'hue complementary thereto, any hue between wave lengths 5000 and 5500 (10.7 I11. m.) and the hue complementary to said last hue.

3. As an article of manufacture, a color re roduction from photographic negatives ta en on four suitab or films, each of a character to be unacted on by a different one of a grou of four fundamental or monochromatic c0 ors, whichvconstitute two of complementary colors (blue and ye ow) and (green. and red).

4. As an article of manufacture, a reproduction in colors produced by photo-mechanical processes in which the negatives are taken on suitable color-sensitive plates or e color sensitive plates tary colors, (blue and ellow and en and red) which are define respective as any hue of the continuous spectrum of w 'te light between wave lengths 4200 and 4900 (10.7 m. m.) the hue complementary thereto, any hue between wave (10.7 m. m.)- and the hue complementary to said last hue.

In testimony whereof I have signed my name to this specification in the presence of twosubscribing witnesses;

CHARLES GUSTAV ZANDER.

' Witnesses:

J OSEPH MILLABD,

WALTER J. MERTEN.

engths 5000 and 5500

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