US3748045A

US3748045A - Color comparator

Info

Publication number: US3748045A
Application number: US00134964A
Authority: US
Inventors: R Mitchell
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-04-19
Filing date: 1971-04-19
Publication date: 1973-07-24
Anticipated expiration: 1990-07-24
Also published as: DE2218917A1; GB1390194A; CA953493A; FR2133847B1; DE2218917B2; FR2133847A1; JPS5128238B1; IT952615B

Abstract

A color comparator providing, in a single device, an expedient and accurate combination of filter media arranged in a generally planar relationship to provide a three dimensional effect portraying the interrelationship of the filter media. The comparator includes neutral density material for providing substantially uniform white light transmission over the entire comparator area and means to facilitate assembly.

Description

United States Patent 1 [111 I 3,748,045

Mitchell a [45] July 24', 1973 I 1 COLOR COMPARATOR [76] lnventor: Robert w. Mitchell, 707 Myrtle 'f' Ave St Joseph, Mich- 49085 Assistant Exammer-F. L. Evans Attorney-Pendleton, Neuman, Williams & Anderson [22] Filed: Apr. 19, 1971 [21] Appl. No.: 134,964

57 ABSTRACT [52] US. Cl 356/191, 355/32, 355/88 [51] Int. Cl. Gfllj 3/52 A color com 1 parator provldlng, m a slngle device, an ex- [58] new ofsearch 6/ l9] |95 355/32 88 pedient and accurate combination of filter media ar- 7 ranged in a generally planar relationship to provide a [56] References Cited three dimensional effect portraying the interrela- UNITED STATES PATENTS tionship of the filter media. The comparator includes 1,769,777 7/1930 Feinberg 356/192 X neutral density material for providing substantially uni- 2,240,05 3 4/1941 Richardson. 356/192 form white light transmission over the entire compara- 3,529,5l9 9/1970 Mitchell 356/191 X tor area and means to facilitate assembly 7 2.l28.676' 8/1938 lves..; ..4l/6 FOREIGN PATENTS OR APPLICATIONS 20 Cl i 15IDj-awing Figures 22,102 ll/l935 Germany 356/194 PATENTEUJUL24 ms SHEEI 1 OF 4 um R mww mm M" IWA BYM,% M

PAIENIEBJUL24|975 3.748.045

' sum 2 0r 4 NEUTRAL DENSITY INVENTOR ROfiE/PT H. MITCHELL aym. z.m was. w

ATTORNEYS PAIENIEDJummn SHEEI 3 (IF 4 mvanron 000501 In mrausu av ATTORNEYS saw u or 4 hi4 l3 FIG.

i LEW .i

INVENTOR ROBERT w. wraps BY I Zena, ,z A

ATTORNEYS I COLOR COMPARATOR BRIEF SUMMARY OF THE INVENTION comparator. Means are also provided to expedite the manufacture of the comparator.

BACKGROUND OF THE INVENTION The arts of color photography, color printing and color processing have grown rapidly in recent years and are now highly developed. Nevertheless, because of the vagaries of color processing, color reproduction and color dyes, precise reproducibility of particular colors under varying conditions and with varying raw materials has been difficult. Depending upon the quality of reproduction required in a given case, highly sophisticated complex and expensive equipment and procedures have been employed to calibrate light sources, original material, processing chemicals and the like.

To simplify these procedures and adapt to the variations in raw materials, various devices have been marketed which will electronically energize light sources and will measure both the optical density and the color characteristics of various original material, sensitive material and the like. These have included simple neutral density diaphanous step wedges to determine the proper exposure time or light intensity during processing. Alternatively, step wedges of color filter material of a given known color have been assembled and used in processingto improve the color rendition in the end product and to compensate for the variations in. light sensitive paper, original material andlprocessing light sources and the like. No single device has been provided heretofore which could satisfactorily be employed, bothby the professional and the home photography enthusiast to quickly and easily calibrate the materials, conditions and original negative or transparency to insure an accurate reproduction.

, OBJECTS OF THE INVENTION It isan object of this invention to provide a simple, accurate and yet inexpensive device which will, when properly used, accurately indicate the filter compensation to be employed in a camera to provide accurate '45 opaque sheet 28 over substantially its entire area.

balanced initial transparencies, in an enlarger or repro-- I ducer to provide color balanced prints or reproductions of the original, in teaching aids, in color display equipment or the like to provide useful color information and optical density information to the user and in any other equipment where an accurate and graphic multicolor standard is desired.

THE DRAWINGS For a more complete understanding of this invention, reference will now be made to the accompanying drawings wherein:

FIG. 1 is a plan view of one color comparator incorporating the features of this invention;

FIG. 2 is a sectional view of the embodiment of FIG. 1 taken along the line 2-2 of FIG. 1;

FIG. 3 is a second sectional view of the embodiment of FIG. 1 taken along the line 3-3 of FIG. 1;

FIG. 4 is a diagrammatic illustration of one use of the embodiment of this invention illustrated in FIG. 1;

FIG. 5 is a diagrammatic view of an alternate use of 7 this invention as it is exemplified in FIG. 1;

FIG. 6 is an exploded view of the color filter portion of the embodiment of FIG. 1;

FIG. 7 illustrates the step wedge assembly forming a part of FIG. 6 and representing one particular hue or color;

FIG. 8 illustrates one means for compensating the embodiment of FIG. 1 to provide substantially uniform white light transmissivity;

FIG. 9 illustrates an alternate embodiment of the color portion of FIG, 1 utilizing six different standard hues;

FIG. 10 is an exploded view illustrating the manner in which the embodiment of FIG. 9 is assembled,

FIG. 11 illustrates one means for compensating the embodiment of FIG. 9to provide substantially uniform white light transmissivity;

FIG. 12 illustrates diagrammatically one technique for efficiently assembling the embodiment of FIG.-6;

FIG. 13 illustrates an alternate neutral density device for the embodiment of FIG. 1;

FIG. 14 is a sectional view taken on the line 14-14 of FIG. 13; and

FIG. 15 is a-sectional view of the embodiment of FIG. 13 taken on the line 14l4 thereof.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, and more particularly to FIGS. 1-5, a color comparator 20, comprising one embodiment of the invention, is shown in FIGS. 1-3 and is shown in position in a light box 22 in FIG. 4. The comparator is shown in use on the easel 24 of an enlarger 26 in FIG. 5. The comparator 20 of FIG. 1 comprises an opaque, rectangular sheet 28 having cutout portions to define the hue measuring area 30: The opaque sheet 20 ispreferably backed with a. transparent flexible sheet" 36 which is sealed to the apertured In the particular embodiment 20 of FIG. 1, a built-up matrix 38 of acetate or gelatin filter media isassembled on top of the opaque base 28 and the matrix is covered over with a transparent film 40. It is contemplated that one of the films 36 or will be formed from photosensitive material which is processed to produce a pattern of neutral density material as described in greater detail below. Each matrix area will have a neutral density which is the complement of the color density of that area.

The thicknesses of the various sheets, films andfilter media shown in FIGS. 2 and 3are highly exaggerated for illustrative purposes and it should be understood that in actual assembly the entire color comparator utilizing present commercially available acetate filters as an example, would be in the order of one-tenth of an inch. Filter media especially designed for this application will presumably reduce the thickness still further. The various areas of neutral density material and color filter media will be secured to the opaque base 20':and the entire assembly will be sealed as a laminated entity with the edges of the film 40, the edges of the:opaque' base 28 and the edges of the lower film 36 being sealed together.

In the preferred embodiment of FIG. 1, the matrix 38 is designed to create the appearance of an orthogonal projection of a cube-like structure having six external corners and a central visible corner 46. The central visible corner 46 will be a patch of neutral density mate- 'rial having a light transmission density corresponding to the white light transmission density of the color filter media at the points where that density is a maximum.

In the embodiment of FIG. 1, the matrix 38 is made up of a plurality of chevron-shaped uniform filter materials 48-56, each of which has the shape illustrated in the exploded view of FIG. 6 and of varying widths. Thus, for example, the chevron-shaped filter media 48-56 of FIG. 6 would all be of a single color or hue, such as, for example, magenta. A similar set of chevrons would be assembled as shown in FIG. 6 with the bight portion of each chevron pointed downwardly to the lower corner 58 of FIG. 6 and all of these could, for example, be cyan. A third set of similar chevron-shaped filter materials would be assembled with the bight portions directed to the upper left-hand corner 60 of the assembly shown in FIG. 6 and this set of elements could, for example, be yellow.

Thus, referring again to FIG. 1, the corner 60 of the color portion of the comparator 20 would be a yellow filter media and the patches lying along the line between corner 60 and center 46 would all have a yellow hue of varying density. Similarly, in FIG. 1, the upper right-hand comer 62 and all patches lying between the upper right-hand corner 62 and the center 46 would have a magenta hue of varying .intensity.

Finally, the lower corner 56 and all areas lying between corner 56 and center 46 will have a cyan hue of varying intensity. All other patches or areas will comprise combinations of any two of the three basic colors involved with the upper corner 64 having a red hue, the lower left corner 66 having a green hue and the lowerright corner 68 having a blue hue.

Each of the rows or diagonals extending outwardly from center area 46 will reflect increasing color densities. In one preferred embodiment of the invention, each of the first four steps reflects an increase of (or .05) of filter density so that the respective steps are 5,

l0, l5 and 20 with the final step at each of the three

corners

56, 60 and 62 being twice the adjacent step or a color density of 40.

As should be clear from FIG. 6, the chevron-shaped materials each have small bight portions which are not covered 'by any other color media thus defining the center neutral patch 46 and three spokes extending to the

corners

56, 60 and 62 which have thereon only the one color associated with the bight portions lying along that spoke. In the preferred embodiment, there is, of course, additional complementary neutral density material.

The manner in which the comparator 20 can be used in practice is illustrated in FIGS. 4 and 5. FIG. 4 shows the comparator 20 assembled in an aperture 70 in the light box 22. The light box includes a reflective wall 72 which is disposed at 45 to receive impinging light rays illustrated by arrows 74. The light rays 74 are reflected from the reflective surface of angular wall 72 and transmitted through the comparator 20. The light may be observed from in front of the light box 22 so that the light rays 74 can be optically evaluated by an observer.

If the center area 46 has the proper neutral gray hue, then the observer would know that the light rays 74 had a neutral or white character and the proper optical temperature for the particular use contemplated. This, of course, depends upon the precise selection of neutral density for the patch 46.

If the observed light through the central patch 46 has a color cast, then the observer can select an alternate area of the matrix which has the desired neutral color and either change the light source accordingly or add filter media in the path of the light rays 74. This can readily be accomplished because of the nature of the color matrix.

For example, if the particular patch which provides a neutral visual effect is disposed in the lower righthand quadrant of the matrix, the observer merely counts the number of squares that the neutral path is below the axis 46-62 and to the right of the axis 46-56 and this immediately indicates the amount of filter compensation required. If, for example, the comparator 20 is constructed using increments of cyan, yellow and magenta of 5 units of density per set, one would merely count the number of steps or sets in each of the three orthogonal directions (never more than two of the three, of course) and add the required amounts of cyan, yellow and magenta, respectively, to correct the light to neutral.

Such a light box 22 can also be constructed with a top cover and an internal light source which may be electrically energized and have appropriate filters disposed between the light source and the front wall and comparator 20. The filters or electrical voltage can then be altered to make desired compensations in the observed colors or to establish a standard light source. Such a technique is valuable in evaluating light sources, in evaluating filter materials, in teaching the theory of light and in various other obvious applications of the equipment.

Furthermore, the light box 22 may be employed for calibrating color reversal film and the like. A camera I 76 may be disposed in front of the box 22 and focused on the front face 78. A test exposure may then be taken with camera 76 and developed in order to calibrate the particular lot of film being employed. If a standard light source has been employed, the transparency, when developed, can be viewed and the color error in the film observed. By merely placing the proper filter on the camera based upon the observation, an accurate color correction of color reversal film can be accomplished.

Another use of the invention is illustrated in FIG. 5. There a piece of sensitive color paper 78 is disposed on the easel 24 of enlarger 26. The comparator 20 is disposed on sensitive paper 78 and exposed to light rays 80 from the enlarger head 82. A film 84 is preferably disposed in the negative tray of the enlarger head and the film should be a photograph of a known neutral gray field so that the light rays 80 impinging on comparator 20 will be of the desired neutral character. When the sensitive paper 78 is then developed, the area corresponding to the central patch 46 should be neutral. If it is not, the proper filter compensation can be readily determined from the printed matrix and filters placed in the filter tray 86 of the enlarger.

If the operator does not have a negative of a neutral gray field, any negative may be employed with a color diffuser such as a frosted glass employed in the enlarger head, either adjacent to the objected lens or at some other point in the'path of projected light 80.

The chevron-shaped elements of magenta filter material 48-56 have identical shapes except that they have a stepped relationship of width so that when stacked, they appear as shown in FIG. 7 with the uppermost element 48 overlying the upper edge of element 50 and in a

similar manner elements

48 and 50 overlying the upper edge of element 52, whereby all of the elements 48-56 have a common aligned edge 88. The elements 50-56 in the embodiment discussed above would each have a color density of 5 while the element 48 would have a color density of 20 and they would all be of an identical magenta hue.

A similar assembly would be made of cyan and yellow media and the cyan and yellow assemblies are already shown in the basic cube at the bottom of FIG. 6.

While the particular densities described above appear to produce optimum results for most applications, any desired combination may be employed. For example, the steps could be 10, 20, 30, 40 and 80, respectively. Whatever steps are selected, it will be apparent that the transmissivity of white light through the matrix will vary from the center of the cube to the six corners and will vary at a more rapid rate at the

corners

64, 66

and 68 where the filter media thicknesses are doubled.

pends upon the desired size and shape of the various areas of color. It is generally desired that the neutral 7 area 110 be enlarged somewhat for easier evaluation tral density material is employed in the matrix. One

technique of using a photographic film having the neutral density pattern was described above. Another technique for incorporating neutral density material is shown' in FIG-8. As shown there, any of the steps 48-56 of the .step assembly can be combined with a complementary neutral density film '94 which, when combined with the step, will fill the'entire hexagon associated with that step. Thus, asthe step depthin creases, the size of the neutral density complement will 'decrease and as the density of the step increases, the density of the neutral portion 94 will also increase cor resp'bndin'gly. A narrow stripof opaque material 96 may beincorporated between the step 48 and the neutrarmediu'm 94 which will produce a narrow white line I l in any print of the comparator. The use of the narrow band 96 to define each area of the matrix is found helprun" performing visual evaluation.

An alternate embodiment of the invention shown in FIGS. 9 and 10 incorporates the three subtractive colors, magenta, cyan and yellow, and the three additive c'olors,red, green and blue, in a single hexagonal configuration. The-particular configuration shown has reand the particular configuration shown servesthis pur-' pose. If desired, each of the six sets of filter material could define straight lines with the pure material falling at the mid point of each line. Such a configuration renders the evaluation and use somewhat more difficult.

The manner in which the five magenta chevrons 98-l06 are assembled together and are assembled with the other five sets can be clearly seen from the ex plodedview of FIG. 10.

One particularly expedient method of assembly is illustrated in FIG. 12. As shown in FIG. 8, each filter 'material of each set may be provided with apertures 112 .in such a manner that proper assembly provides align-' ment of the apertures. The color and neutral density materials 48, 94 and the. like are assembled over a set of spaced pins 114 which are. mounted on a base 116.

As can be seen in the particular embodiment, each color material will have three apertures and each neutral density material will also have three apertures and alignment will be assured. Furthermore, one of the

transparent cover films

36 or 46 may be imprinted with the entire matrix of lines 46or produced photographically and also be apertured to provide positive index- As each layer is constructed, the spokes of the neutral material 32 would become wider while the legslof the

color materials

118, and 122 wouldbecorne narrower. i

' Instead of assembling'the neutral density material in the manner illustrated in FIG. 8, it is contemplated that the transparent backing 36 of FIG/2 can be formedin tegrally with the various neutral density areas andbe' a photographically produced complementary pattern, a preformed Iamina'teor a molded product. One such configuration is shown in FIGS 13-15,. In the configuration, of FIGS. 13-15, every area'of the color matrix 38 has a thickness or neutraldensity corresponding to the complement of thecolor filter density and, thus, provides a unique area l'24'-l40,"etc.," or diminishing density from the center outwardly in all directions.

'As shown in FIG. 15, the section through the right hand column of areas shows that the areal42 hasa thickness or density half that of the center area 124and each area there below 144-150 has a density or thick.

ness half that of thecorresponding area in the center As will be apparent from the foregoing, this invention provides a novel device for colorimetry inwhich aisirnple visual inspection of an orthogonal projection of 'a cube on a planar surfaceor a similar display of spatially related color areas enablesquick, accurate and'-inexpensive color evaluation. By incorporating complementary neutral density material, the accuracy OfiStIGh' evaluation is greatly enhanced.

fully explain the character of the invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, while retaining certain features which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured by the following claims.

I claim:

1. A color comparator comprising a supporting base defining a central aperture and a plurality of partially overlapping similarly shaped diaphanous color elements supported thereon and partially overlying said aperture, said plurality of color elements including at least one set of color elements, each set including at least one color element of each of a plurality of different colors with all of the color elements of said set having substantially the same predetermined color density, each color element having a central portion and two oppositely disposed end portions, all of the color elements in a set being arranged in a single logical end-to-end closed pattern with said end portions of said elements in overlapping relationship to provide predetermined color combinations thereof disposed within said central aperture.

2. The color comparator of claim 1 wherein said base and said color elements are diaphanous.

3. The color comparator of claim 1 wherein neutral density transmission means overlie said color elements between the ends of said color elements which overlie the corresponding ends of adjacent color elements whereby the entire comparator has a substantially uniform effective transmission density.

4. The color comparator of claim 1 including at least two sets of color elements each set having a plurality of elements having colors corresponding to elements in the remaining sets, said sets being in an aligned relationship with the corresponding colors thereof aligned side-by side, one of said sets having a color density less than that of the adjacent of said sets by a predetermined increment of color density.

5. The color comparator of claim 4 wherein the ends of the elements of each of said sets effectively overlap all of the elements of the adjacent sets.

6. The color comparator of claim 4 wherein neutral density transmission means overlies said one set of color elements whereby said one set and said adjacent set of color elements have'a substantially equal effective transmission .density.

7. The color comparator of claim 1 wherein said set comprises three color elements.

8. The color comparator of claim 7 wherein the colors of said color elements are cyan, magenta and yellow.

9. The color comparator of cliam 7 wherein the colors of said color elements are red, blue and green.

10. The color comparator of claim 1 wherein said set comprises six color elements.

11. The color comparator of claim 10 wherein the colors of said color elements are cyan, magenta, yellow, blue, green and red.

12. The color comparator of claim 1 wherein each of said color elements is an elongate element having two end portions disposed at an obtuse angle and a bight portion.

13. The color comparator of claim 5 wherein each of said sets comprises color elements of cyan, magenta and yellow.

14. The color comparator of claim 11 wherein each of said color elements is an elongate element having two leg portions disposed at an acute angle and a bight portion, the end portions overlying end portions of adjacent elements in the sequence: blue, cyan, green, yellow, red and magenta.

15. The color comparator of claim 14 wherein said overlying ends extend outwardly and said bight portions extend inwardly to define a six-pointed star and the center of said comparator has a neutral density, neutral density material overlying each intersection of two elements except the outer-most intersection at each point of the star and overlying said center to provide substantially uniform transmission of white light over the area of said comparator.

16. The color comparator of claim 5 wherein each of said color elements is formed of filter material having an area corresponding to the area of said element and an appropriate transmissive density and hue, said material being assembled in a generally planar arrangement on said base to provide the desired hues in each overlapping area of said elements. 7

l7. Thecolor comparator of claim 5 comprising a plurality of pieces of color filter material, one piece corresponding to each color of each set, the area of each piece of a given set being the area of the corresponding color element of the set plus the area of the color elements of the corresponding color of each set having a color density greater than said given set and the color density of said piece being equal tothe color density corresponding to said given set reduced by the color density of all less dense sets.

18. The color comparator of claim 17 including a plurality of sets, each having an increase of color density from the inner adjacent'set, allof said increases being equal, and an outermost set having a color density twice that of the adjacent set.

19. A diaphanous color comparator comprising a supporting base defining a central aperture and a plurality of partially overlapping similarly shaped diaphanous color elements supported thereon and partially overlying said aperture, said plurality of color elements including at least two sets of color elements, each set having a plurality of elements having different colorsand corresponding in color to corresponding elements in the remaining sets, said sets being in an aligned-relationship with the elements having corresponding colors thereof aligned, and all of the color elements of any set having substantially the same color density, each of said color elements having two elongate leg portions and a bight portion, the elements of each set being arranged in a single logical, end-to-end closed pattern with leg portions in'overlapping relationship, each set of elements having a color' density less than the adjacent set and theoutermost sethaving the greatest color density whereby the visual effect created by said comparator is that of a single diaphanous geometric pattern of a plurality ,of different colors disposed about the periphery of said aperture in said base and a plurality of different color densities of increasing magnitude extending outwardly from the central portion of the comparator and inwardly from the periphery of said aperture.

20. The color comparator of claim 19 wherein said leg portions are disposed at about relative to one another and each of said sets includes three elements of different colors, the elements being arranged to produce a visual effect of an orthographic projection with a neutral density appearing centrally in the comparator.

i i t I?

Claims

1. A color comparator comprising a supporting base and a plurality of partially overlapping similarly shaped color elements supported thereon, said plurality of color elements including at least one set of color elements, each set including at least one color element of each of a plurality of different colors with all of the color elements of said set having substantially the same predetermined color density, each color element having a central portion and two oppositely disposed end portions, all of the color elements in a set being arranged in a single logical end-to-end closed pattern with said end portions of said elements in overlapping relationship to provide predetermined color combinations thereof.

4. The color comparator of claim 1 including at least two sets of color elements each set having a plurality of elements having colors corresponding to elements in the remaining sets, said sets being in an aligned relationship with the corresponding colors thereof aligned side-by-side, one of said sets having a color density less than that of the adjacent of said sets by a predetermined increment of color density.

6. The color comparator of claim 4 wherein neutral density transmission means overlies said one set of color elements whereby said one set and said adjacent set of color elements have a substantially equal effective transmission density.

15. The color comparator of claim 14 wherein said overlying ends extend outwardly and said bight portions extend inwardly to define a six-pointed star and the center of said comparator has a neutral density, neutral density material overlying each intersection of two elements except the outermost intersection at each point of the star and overlying said center to provide substantially uniform transmission of white light over the area of said comparator.

16. The color comparator of claim 5 wherein each of said color elements is formed of filter material having an area corresponding to the area of said element and an appropriate transmissive density and hue, said material being assembled in a generally planar arrangement on said base to provide the desired hues in each overlapping area of said elements.

17. The color comparator of claim 5 comprising a plurality of pieces of color filter material, one piece corresponding to each color of each set, the area of each piece of a given set being the area of the corresponding color element of the set plus the area of the color elements of the corresponding color of each set having a color density greater than said given set and the color density of said piece being equal to the color density corresponding to said given set reduced by the color density of all less dense sets.

18. The color comparator of claim 17 including a plurality of sets, each having an increase of color density from the inner adjacent set, all of said increases being equal, and an outermost set having a color density twice that of the adjacent set.

19. The color comparator of claim 1 wherein said base is apertured and said color elements overlie the aperture in said base.

20. The color comparator of claim 1 wherein said color elements are diaphanous.

21. A color comparator comprising a supporting base and a plurality of partially overlapping similarly shaped color elements supported thereon, said plurality of color elements including at least two sets of color elements, each set having a plurality of elements having different colors and corresponding in color to corresponding elements in the remaining sets, said sets being in an aligned relationship with the elements having corresponding colors thereof aligned, and all of the color elements of any set having substantially the same color density, each of said color elements having two elongate leg portions and a bight portion, the elements of each set being arranged in a single logical, end-to-end closed pattern with leg portions in overlapping relationship, each set of elements having a color density less than the adjacent set and the outermost set having the greatest color density whereby the visual effect created by said comparator is that of a single geometric pattern of a plurality of different colors disposed about the periphery of said comparator and a plurality of different color densities of increasing magnitude extending outwardly from the central portion of the comparator.

22. The color comparator of claim 21 wherein said leg portions are disposed at about 120* relative to one another and each of said sets includes three elements of different colors, the elements being arranged to produce a visual effect of an orthographic projection with a neutral density appearing ceNtrally in the comparator.