Note: Descriptions are shown in the official language in which they were submitted.
~'7~B~3
Background of the Invention
.... _
Field of the Invention
. . _ . . _ . . .
The present invention relates in general to the field
of synthesizing colors on photographic media by the successive
exposure thereof to an illuminan-t source through a group of up
to three color filters for selected times for each desired
color. More particularly, the method of the present invention
relates to the art of preparing and using a color reference
diagram or like data base to assist in determining the il-
lumination exposure time needed for each of up to three colorfilters for each desired colorj as disclosed in our Great
Britain Patent No. 1,592,839, entitled Method of Obtaining a
Target Colour On Colour Photosensitive Pho~ographic Material,
and then utilizing such exposure times to produce a single
sheet pre-press color proof from color separation negatives
or the like.
Description of the Prior Art
Conventional prior practice with respect to color
proofing in the printing trade essentially involves either
actual press proofing ~a procedure where actual test print-
ing plates are made to literally color print the proof) or
by use of primary color and black transparent overlays.
For example, 3M Company markets, un~er the trademark
"Color-Key", pre-press proofing materials involving pre-
sensitized ink pigment coatings, in either transparentor opaque colors, on transparent polyester base sheets.
x7~8~3
Each pi~ment coatin~ is intended -to be correla-ted with
various process color printing inks. ~ach primary color
and black "Color-Key" sheet is overlaid by its associated
separation negative and after exposure and development,
the four "Color-Key" sheets are overlaid in register to
provide a "proof" or simulation of what the four-color work
will look like when printed. ~lanifestly, such a pre-press
proofing system, involving four overlaid sheets (which are
glossy in character and which at best only indirectly match
the colors of the proof with ~-he actual colors of the print-
ing inks to be used) falls well short of providing the user
with a fully accurate proof in the sense of the colors, color
registry and texture of the color work when press printed
with inks on paper.
3M Company also markets a pre-press color proofing
system under the trademark "Transfer-Key", which is said
to provide a complete four-color proof on a single sheet.
In this system, fac-tory pre-coated carrier sheets of color
pigmentj respectively beariny cyan, yellow, magenta and
black pigment, are successively manipula-ted to lamina-te each
pigmen-t onto the base material by use of a proprietary
laminator. Specifically, the cyan pigment is first laminated
to the base material, which is then exposed to the cyan
separation negative and the sheet then developed in a
proprietary processor. The same exposure/development,cycle
is repeated with each color, producing the four-color proof.
Pre-coated pigment carrier sheets are available only in
certain colors, unless specially ordered. As manifest, such
color proofing procedure, although providing a single sheet
color proof, is of limited applicakility and accuracy in that
--3--
~'7~
only certain laminating pigmen-ts are available, and is
inherently rather slow in cycle time in -that each pigment
layer of the four-color proof must be separately and
successively laminated, exposed and developed.
Another commercially available pre-press color
proofing system is marketed by the duPont Company, under
the trademark "Cromalin"~ In the Cromalin color proof
system, dry pigment toners are factory "calibrated" to
printing ink colors and each primary and black color repro-
duction is on a separate sheet of photopolymer film, the
films after exposure and development being laminated together
in registry to provlde the color proof. The cycle time Eor
this system is said to be "within an hour", rather than the
hours or days required for press proofing.
Another known pre-press color proofing system which
is commercially available in the Kodak Polytrans Colour
Proofing Film System, such as described in "The Reproduction
of Color", by R. W. G. Hunt, at page 546 (published by
Fountain Press o~ Hertfordshire, England, Third Edition,
1975). In the Polytrans sys-tem screened color separation
films are proofed by materials including films consisting
of color-pigmented photopolymer matrices coated on a trans-
parent film base. Exposure to blue or ultraviolet light
hardens the photopolymer so that exposure thereof to the
screened separations results in an image-wise pattern of
the hardened polymer being obtained. Each exposed film
is mounted on a sui-table roller and rolled under heat and
pressure onto a sheet of paper, the unhardened polymer
transferring to -the paper and taking the pigment with it.
Four different colors of film are used and, by exposlng each
7 ~
to the corresponding color separation positive, image-wise
transfers can be obtained in each color. Each image is
developed and transferred in succession, onto the paper, in
register, with a color proof resulting after exposure of
the transferred pigments to light. While the Polytrans
system results in a color proof on a single sheet of paper,
the color-pigmented photopolymer matrices used are necessarily
precalibrated to printer's inks at the factory, and each
color is separately and successively developed on the color
proof. Registr~ of the respective color images on the paper
can also prove to be a problem because the color images are
applied to the paper by successive roller transfer.
Brief Summary of the Invention
In general, the present invention involves the
method of obtaining the color proofing target colors from
an illuminant source on a single sheet of photographic media
or the like by preparing a color reference diagram or like
data base characteristic of a given illuminant source (in
the manner taught by our aforementioned Great Britain Patent
No. 1,592,839; using the color reference da~a base to aid
in determining the exposure times -to use with each of up
to three color filters for each target color; exposi,ng the
photographic media through the color filters for their
respective exposure times; and then developing the exposed
photographic media to produce a pre-press color proof.
Another characteristic of the present invention is
the providing of a relatively simple, inexpensive method of
-? -5-
~7~8~3
synthesizing color proofing target colors by sequentially
exposing a photographic media to llght of different colors
which is extxacted from an illuminan-t source by color filters
and which is applied to selected porti~ns of the photo-
graphic media, as by sequen-tial exposure through a set of
color separation ~ilms.
Further objects and features of the present invention
involve the development and use of a color reference data
base for accurate color reproduction of color proofing
target colors on photographic print media by use of an
illuminant source and sets of color filters, which data
include and interrelate (1) the chromaticity coordinates,
dominant wavelength, and saturation percentages for each
possible target color in relation to the given illuminant
source, and ~2) the chromaticity coordinates and filter
percentage characteristic of each filter for each target
color in relation to the illuminant source. Optionally,
the data can also include, or can in part be expressed in
terms of target color densities, i.e. the gray level and
the proportionate levels of red, yellow and blue in each
target color.
More specifically, it is an object and feature of
the present invention to provide a method whereby pre-press
color proofs may be rapidly, economically and accurately
prepared on a single sheet of opaque photographic paper to
show what the color reproduction will be like when printed
using a given set of printer's inks and plates prepared from
a given set of color separation films, -the color proofing
technique of the present invention offering the unique
advantage of being able to directly utilize swatches of the
8B
actual prin-ter's inks as targe-t colors in -the process and
requiring only a single s-tep of photographic media develop-
ment rather -than separate development s-teps for each color,
as is characteristic of prior art pre-press proofing sys-tems.
The technique of the present invention realizes marked
improvement in color proofing cycle time. The apparent
capability of the present process in this respect is a
cycle time of about fifteen minutes or even less, as com-
pared with a cycle time of about an hour for previously
known pre-press proofing processes, and as compared with
a cycle time of at least several hours when using con-
ventional press proofing techniques.
These and other objects, features, advan-tages and
characteristics of the method of my present invention will
be apparent from the following detailed description of the
preferred embodiments thereof in which reference is made
to the accompanying figures.
Brief Description Of The Drawings
FIG. 1 is a block diagram outlining typical appli-
cation of the present invention to pre-press color proofing.
FIG. 2 is a block diagram outlining a typical color
printing procedure including the production of a color proof
from a given set of four-color separation films and a given
set of printer's inks and printer's paper or the like, in
accordance with the present invention.
'7~
Description of the Preferred Embodiments
The present invention i5 in some respects an application
and improvement of the target color reproduction method
disclosed in our a~orementioned Great Britain Patent No.
1,592,839. For discussion purposes, a brief overview of
such target color reproduction method is set forth below,
along with a discussion of some of the method's underlying
prlnciples .
Preliminarily, it may be assumed that every color
visible to the human eye is composed entirely o red, green
and/or blue components. Thus, it fcllows that any such color
may be synthesized by the proper additive mixing of red,
green and blue lights. However, the problem remains of
how to determine what are the red, green and blue components
of a given tar~et color, and how to select and use color
filters which will extract the proper amounts of red, green
and blue light from a given illuminant source to reproduce
that color on the particular photographic media being used.
Since, as has been explained, the color temperature
of the illuminant source is a basic factor which must be
considered, the starting point ~or a given target color
reproduction is to determine the Kelvin temperature o~ the
illuminant source which will be used to produce the target
color. Having determined the color temperature of the
illuminant source, it may then be located as by plotting
thereof on a data base such as a CI~ diagram working area.
Next, the target color data point is determined in
the data base working area ~or the color to be achieved.
.~ .
This is done by comparing the target color to a color
reference data base which was prepared with an illuminant
source having the same color -temperature and spectral
distribution as the illuminant source being used -to produce
the target color. The location of the closest matching
color on the data base, e.g. the coordinates of the matching
color on -the color reference diagram is taken to be that of
the target color.
Then, a set of three filters is selected which can
be used to produce the particular target color. Filter
triangle plots, or data base equivalent ~hereof, are then
delineated and any set of three filters may be used which
defines a Eilter triangle or equivalent coincident with
the location of the target color. This is because, when
considering photographic media, a set of three filters
may be used to produce any color located within or on the
filter triangle they define.
Once the red, green and blue components (x, y and z)
of the target color and of each of the three color filters
are known, a determination is made as to how much of each
color filter is needed in order to produce the target color.
This is done by determining what percentage of each color
filter (i.e. what filter percentage) is needed to achieve
a result such that the sums of their red, green and blue
contributions equal, respectively, the red, green and blue
components of the target color.
Each filter's exposure time is next determined by
multiplying its respective saturation time by its respective
filter percentage. Finally, the particular, positive photo-
graphic media being used is exposed sequentially to theilluminant source through each color filter for its respective
~'7~8~
exposure time. Upon developing the photographic media in
accordance with the manufacturer's instructions, the target
color is produced on the developed positive photographic
media.
To further illustrate the significant features of
our earlier disclosed target color reproduction method,
the following detailed example thereof is presented. A
swatch of a bluish color was chosen to be the color for
reproduction, i.e. as the target color.
A color reference data base in the form of a CIE
diagram was produced according to the procedure set forth
in our said Great Britain Patent No. 1,592,833, with the
same illuminant source as that of the illuminant source
being used to prepare the target color (tungsten at 3050 K.).
Then, the target color was compared to the color reference
data base and it was noted that the x, y coordinates of the
closest matching color thereon were x(red) = .211 and
y(green) = .3425. Using these coordinates, a point for the
target color was plotted on the working diagram. In connection
with the working diagram it will be understood that such a
diagram may be of the CIE type or may be any Cartesian
coordinate system or equivalent data base, such as a computer
program, having units which can be correlated with those used
in a standard, CIE diagram. For example, a known data system
involving programming a digital computer to determine CIE
coordinates from spectro-photometric data is disclosed by
J. E. McCarley et al. in an article entitled "Digital System
for Converting Spectro-photometric Data to CIE Coordinates,
Dominant Wavelength and Excitation Purity, at 55 Journal of
The Optical Society of America, pp 355-360 (April, 1965).
Other data systems known per se may also be used without
departing from the scope of the present invention.
, --1 0--
88
In the example being discussed, three color filters
Kodak (trade mark) Wratten Photomechanical filters 25 (red),
58 (green) and 47B (blue) were selected and located in the
data base, either by use of the manufacturer's reference data,
or by use of a spectrophotometer, or by direct comparison of
the colored filters to the color reference diagram to find
the coordinates of the closest matching color thereon, for
example.
For the three filters selected, the following coordinates
were supplied by the manufacturer:
Filter x (red) y (green) z (blue)
25 (red) .6850 . 3147 . 0003
58 (green) .2693 .6831 .0476
~7B (blue) .1554 .0220 .8226
The saturation time for each color filter was determined
for the particular, positive photographic paper being used
Kodak (trade mark) Ektachrome (trade mark) RC paper type 1993,
manufactured by Eastman Kodak Company. In the example
selected, the saturation times for the red, green and blue
filters were found to be, respectively, 35.3 seconds, 37
seconds and 20.1 seconds.
Afte the saturation times have been determined for
each filter, a final check on the accuracy of the result can
be made by trial production of a gray at the plotted point
for the illuminant source. Whether a gray has been achieved
may be checked, for example, by comparing the resulting
color with a standard reference work such as the True Color
Process Guide, published by Krug Litho Art Co~, of Kansas
City, Missouri, or by checking the sample on a reflective
digital densitometer such as a GAM Model 126P, available
from the Graphic Arts Manufacturing Company. If it i5
, . ~
found that a ~ray has not been achieved, the dominant color(s)
are observed and the exposure time(s) for the fil-ter(s) are
adjusted, as is known to those skilled in the ar-t, until a
gray is obtained.
Next, the filter percentayes for the red, green
and blue filters, in relation to the target color were found
to be 0%, 48.1%, 51.9%, respectively. These filter percen-
tages (the proportiona-te filter exposures necessary to
essentially reproduce the target color from the filter
colors) can be obtained by interpolatively correlating the
target color coordinates and the filter color coordinates.
Thus, for example, the dominant filter 47B (blue) can be
expected to provide the dominant target color component
(z coordinate .4465) and will approximately do so at a filter
percentage of 52% (.4465 - .42775 = .01875 error). Similarly,
the second significant color coordinate of the target color
(y coordinate .3425) can be provided primarily by the filter
58 (green) which it will approximate at a filter percentage
of 48%, taking into account the y component (yreen) contri-
bution (.0114) of -the 47B filter (blue) (.3425 - .0114 - .3279
= .0032 error), with this filter 58 (green) also substantially
providing the third target color component (x coordinate .2110)
at the same filter percentage along with the x (red) component
contribution (.0808) of the 47B filter (.2110 - .0808 - .1293
= .0009 error), and making a z component (blue) contribution
(.02285) reducing the blue error in -the 47B and 58 filter
contributions (.01875 - .02285 = -.0041 error). Refinement
of the interpolations results in the indicated respective
filter percentages for the selected filters, in relation to
the selected target color, of 0% for the 25 fil-ter (red), 48.1
for the 58 filter (green), and 51.9% for the 47B Eilter (blue).
-12-
By multiplying the red, green and blue filters' respective
filter percentages by their respective saturation ~imes, the
desired exposure times for the respective filters were found
to be 0 seconds, 17.8 seconds, and 10~4 seconds, respectively.
The undeveloped photographic paper is then exposed to
the illuminant source through each of the up to three color
filters for its respective exposure time. After the last
exposure is madej the positive photographic media is developed
in accordance with the manufacturer's instructions, with the
result that the target color is obtained on the developed
photographic paper.
A technique important to practical target color repro-
duction involves the determination of saturation time for a
particular gray level, since this gives the base time for all
colors on that level. This determination is made as follows:
A trial exposure is made for a gray sample, using any combination
of up to three ~ilters, but the filter combination should be
such as io produce a color balance of 1/3 each of cyan, magenta
and yellow. The exposed sample, which involved negative print
paper Kodak (trade mark) 37 RC as a further illustrative example,
is then measured with a densitometer or like instrument (spec-
trophotometer or colorimeter) -that identifies balance of cyan,
magenta and yellow, i.e. the grayness of the sample. In
the case where a densitometer is used for this measurement,
four readouts are given by the instrument. As an example~
the gray level of the sample may be 70 and the color aensities
may be cyan 65, magenta 72 and yellow 59. By adding these three
densities, a total of 196 results. Since a color balance is
desired, i.e. a relative density of .33 .33 .33 of a density of
65 65 65, we note that the density balance in the selected
example is 33% for cyan, 37% for magenta and 30% for yellow.
In the instance of this example, these colors were obtained
through the complementary filters Wratten 25, 58 and 47-B,
;~ r 13
for cyan, magen-ta and yellow. Subtracting the percent
difference for each color, i-t is no-ted that cyan at 33~
requires no correction, the magenta requires a reduction
of -4~ and yellow requires an increase of +3%. At this
point a correction factoring system is employed to make
a new exposure. In the correction system adopted in this
example, -the correcting number (on a geometric progression
scale) to reduce the magenta density by 4% is .9120. This
number is then multiplied by the original exposure -time, which
gives a new time for the magenta exposure. Correspondingly,
yellow is 3~ under so the correction factor in this instance
would be 1.072 to give the new exposure time for yellow.
If it is preferred that the gray level be a differen-t
figure, say 66 by way of example, instead of 70, the correction
figure to arrive at the preferred gray level is .942857,
applicable to all exposure times. Another sample is exposed,
using the revised exposure times and the correc-tion procedure
is repeated if necessary until the desired gray balance and
gray level are achieved. Once these exposure times are
obtained it is next desirable to find -the saturati.on time
for that level for all colors. With the correct gray exposure
time at hand, the three exposure times are divided by the
correct "percentage of filter" amounts for gray, as determined
from the chromatici-ty data base for the illuminant point, as
earlier discussed.
Taking the "percentage of filter" amounts for the
illuminant point, these figures are divided into the new
times for gray and this determines the satura-tion times
for this particular level of the chroma-ticity diagram
for all colors. Using this time, any color can be achieved
-14-
,y multip:lying its "percentage of f'ilter" amount by the
s~turation time.
To iLlustrate this technique, and using the
example initially discussed earller, the following measure-
ments and calculations occur:
1. Time used 10.1 sec. for the 25 filter (for cyan)
4.2 sec. for -the 58 filter ~for magenta)
2.4 sec. for the 47-B filter ~or yellow)
2. Sample measured 70) 65 72 59
3. 65-~72~59 = 196 65/196 - 33% 72/196 7 37% 59/197 = 306
4.NEED 33%NEED 33%NEED 33%
HAVE 33OHAVE 37~ H~VE 30%
0 + 4% - 3%
5.-6. .9120 1.072
X 4.2 X 2.4
10.1 3.8 2.6 NEW TI.~E
7. NEED . 66 gray level
HAVE . 70 " " .66/.70 = .942857
10.1 3.8 2.6
X.942~57 X.942857 X.942857
9.5 3.6 2.4 NEW TIMES for .66 gray
10. Assuming that -these'times for gray are correc-t, the
following SATUR~TION TIMES FOR the .66 level of the
chromaticity diagram evolve, using the given photo-
graphic media used in the example:
9.5/.443458 = 21.4 sec. 3.6/.379670 = 9.4 sec.
2.4/.176872 = 13.56 sec.
Any color can now be exposed for,using these times.
the complement of
Thus, for/a dominant wavelength of 410 at the 90% saturation
level from the illuminant, can be computed by
.083369 .003930 .912701
X21.4 X 9 4 X 13 45
1.8 ~ 04 12.3
As will be evident, the determinations and operations
of the exposure equipment can also be accomplished by computer,
utilizing programming techniques known per se. In one pro-to-
-15-
7~
type equipment at hand, an Apple II (trade mark) computer i5
used with a so-called ~, y table to horizontally move -the photo-
~raphic media under a stati~nary mask opening through which the
media is ill~lminated downwardly from a stationary illuminant
source through selected filters. The computer also inter-
faces with exposure control mechanism, i.e. the light source
and filters. In the phototype arrangement a computer is
used with a color TV monitor. All necessary computations to
provide the color reference data base for the light source
and filters are programmed into the computer in a manner
known per se. The photographic media is moved on the x, y
table under control of the computer so that the desired
exposure point is directly in line with the mask openiny and
the light source. Filters are moved into line with the
illuminant source sequentially and exposure times are also
controlled by the computer to reproduce any desired target
color in the manner characteristic of the present invention.
Repeated exposure to develop an array of target colors can
result in an entire data base working area being produced~
As earlier indicated, the present invention lnvolves
the application of the foregoing target color reproduction
method to the field of color printing and specifically to the
proofing, prior to the making of printing plates, of the
so-called color separation components (film negatives or
positives) from which the plates are to be made. Given a
set of color separation films and a given set of printer's
inks (e.g. yellow, magenta, cyan and black), the present
invention provides, through use of photographic printing
techniques, a simple and accurate way of determining what
-16-
7~
printed color reproductions will look like without actually
having to prepare test printing plates. More specifically,
the present invention provides a simple and straightforward
pre-press color proofing technique whereby a given set of
color separation components is "proofed" on photographic paper
in a manner showing what the printed color reproduction will
be like if printed with a given set of printer's inks, the
color proof being "printed" by use of a light source and
color filters rather than by use of the inks, with filtered
light exposure times coordinated to the ink colors.
In making of color proofs from color separation com-
ponents in a manner according to the present invention, each
separation component (which is a black film base, positive or
negative), may be considered simply as a mask con-trolling the
areas or portions of the photographic print paper which are
exposed to selected sets of filters for selected times
simulating the color composition of the inks. ~y this
technique, the "printing" of the photographic paper is ac-
complished by light in essentially the same manner as a printer
would print with inks, i.e. with all colors "printed" on a
single non-transparent sheet of paper, as distinguished from
conventional color proofing techniques which commonly involve
each primary color and black being developed on separate
transparent sheets which are superimposed to simulate'the
final printed reproductions.
As a specific example of application of the present
invention, it will be understood at the outset tha-t color
separation components, as made or available in -the color print-
ing field, are derived in a number of ways, such as through a
j, ,;
~ 17-
camera process, conventional per se, which provides four
color separation films, each of which in appearance is a
black film base, positive or negative, but which constitutes
respective records of the yellow content, -the magenta con-
tent, the cyan content, and the black con-tent of the original.
Each such black base film is in effect a mask made of more or
less microscopic dots or continuous tone which either parti-
ally pass (a negative film) or partially block ~a positive
film) light in the course of preparing the corresponding
color printing plate to be used in the final printing process.
Each such "dot" or "tone" of the printing plate permits more
or less of the corresponding ink to be applied to the paper
on which the printed color reproduction is printed.
As diagrammatically illustrated in FIG. 1, to obtain
a color proof of what the printed color reproduction will be,
using a given set of inks and a given set of color separation
components, the printer or color proofer, in utilizing the
concepts of the present invention, first makes so-called
"draw down" samples of the four inks on the paper or like
base which is identical to or at least similar in color
and texture to the paper or base on which the printing run
is to be made. These are simply samples or "swatches" of
the yellow, magenta, cyan and black inks which the printer
has tentatively selected for the printing. Each ink s,watch
thus produced is then subjected to color analysis, as by
comparison with a color reference data base developed and
applied as taught by our aforementioned Great Britain Patent
No. 1,592,839 to determine in each instance the red, green
and blue components thereof, and up to ~hree color filters
are selected in each instance from which the color of each
^; -18-
ink swatch, as a color proofing target color, can be reproduced
from a given light source. As will be understood, with a
given light source and with four swatches of a selected set
of ink candidates (yellow, magenta, cyan and black), the
analysis technique of the present invention provides the
color proofer with information as to the identity of each
of the up to three color filters to be used in the
reproduction of each of the four target colors (the ink
swatches), and the light source exposure times to be used
with each of the color filters to reproduce each of the
four target colors.
With this information at hand, a selected photographic
print paper (such as Kodak (trade mark) Ektacolor (-trade mark)
RC 74 negative print papex, for example) is placed on pins in
the exposure plane associated with the light source and filters
(the pins matching pin holes in the separation films). The
first (e.g. yellow) separation film is then placed on the un-
exposed photographic print paper and the light source and first
group of filters (e.g. the yellow group) ar~ controlled to expose
the photographic print paper and first (e.g. ~ellow) separation
film to the light source in sequence through the associated up
to three filters for the determined illumination times to re-
produce the first ink target color image on the photographic
paper when the paper is developed. The first separatlon film
is then removed from the print paper, the second separation
film (e.g. magenta) is superimposed on the paper, and the
exposure process is repeated using the second group of up
to three filters te.g. the magenta group) and the associated
exposure times determined for the second (e.g. magenta) ink
swatch. The second separation film is then removed from the
. ... .
--19--
~73~8~
photographic paper and the third (e.g. cyan) separation film
superimposed thereon, with the e~posure sequence again
repeated using -the up to three color fil-ters of the third
group of fil-ters (e.g. the cyan group) and the associated
exposure -times determined from the target color analysis
of the third (e.g. cyan) ink swatch. The third separation
film is -then removed from the photographic paper and the
fourth separation film (e.g. black) superimposed thereon,
with the exposure sequence again being repeated with the
up to three color filters of the fourth group of filters
(e.g. the black group~ and the associated exposure times
determined for the fourth (e.g. black) ink target color
swatch.
The resulting photographic paper, thus exposed, is
developed in the conventional manner, and the resulting
developed print is an image-wise color proof on a single
sheet of opaque paper, accurately showing the color proofer
what the finished printed color material will look like
when printed on the selected paper by use of the selected
inks and printing plates prepared from the selected separation
films, it being significant in this respect that the color
proof is thus produced without test plates and wi-thout ac-tual
use (beyond the preparation of the original ink swatches)
of the inks to be used on the paper to be used in the final
25 color printing. `
As a specific example of practice of the present
invention, a set of color separation films was prepared
from a graphic art overlay of a ci-ty tourist map and related
text material. The separa-tion films were produced by
compositing various screen effects into four color separation
negatives in a known manner. ~pecifically, various color
-20-
effects were developed on GAF (trade mark) P4 20x24" line
negative film, following which the color ef~ects were composited
on GAF (trade mark) HD 403 duplicating film ~or the four
color separation negative films. Target color samples were
obtained from the prin~er on coated web stock white paper
(50 lb.) which were draw downs of the four inks to be used
in the printing of the maps, namely, Acme Temp (trade mark)
Yellow M-76325-A, ~cme Temp (trade mark~ ~roc. Warm Red M-79535,
Acme Temp (trade mark) Blue M-76326 and Acme Temp (trade mark)
Black M-76990. The available illuminant light source was a
GE tungsten map lamp rated at 100 watts at 20 volts, and the
temperature thereof was measured to be 3050 Kelvin by a
Gossen (trade mark) color temperature meter. The primary
color components of the various samples were then measured by
a GAM (trade mark) reflection densitometer, Model GAM 126P.
The yellow ink sample was found to have a gray level of 13,
a density (proportiona~ percentage) of 23 (13.6%) for blue,
30 (17.8%) for magenta, and 116 (68.6%) for yellow. The
magenta or warm red sample was found to have a gray level of
45, a density of 29 (11.3%) for blue, 134 (52.3%) for mayenta,
and 93 (36.3%) for yellow. The cyan or blue sample was found
to have a gray level of 96, a density of 151 (60.2~) for blue,
64 (25.5~ for magenta, and 36 (14.3%) for yellow. The black
ink sample was found to have a gray level of 189, a density
of 193 (33.2%) for blue, 193 (33.2%) for magenta, and 196
(33.6%) for yellow.
The x, y and z coordinates of the ink samples were
determined by reference to a data base (as in our Great Britain
Patent No. 1,592,839), or such can be determined directly by
use of a spectrophotometer, as follows:
,,r.~g
~ 21-
7~8~3
Ink Sample x y z
yellow .4973 .4614 .0275
magenta .6107 .3312 .0579
cya~ .2245 .3193 .4560
black .4597 .4063 .1338
In this example, the filters chosen were the same
as employed in the earlier example set forth, namely Kodak
(trade mark) Wratten Photomechanical Filters Numbers 25 (red),
58 (green), and ~7B (blue). In this example, the selected
undeveloped photographic paper was Kodak (trade mark)
Ektacolor ~trade mark) RC 78, type NRC, manufactured by
the Eastman Kodak Company. For this paper, the saturation
times, adjusted as to each gray level, were determined as
earlier set forth, for the red, green and blue filters, to be:
Filter 25 Filter 58Filter 47B
(red) (green) (blue)
.. . . __
For gray level:
13 (yellow) 3.5 sec. 8.2 18.3
45 (magenta) 41.8 28.3 63.5
2096 (cyan 89.2 60.4 135.4
189 (black) 175.6 118.9 266.7
From the determined information as to the color
component makeup of the samples, the characteristics of the
available primary color filters, and the nature and saturation
times of the given photographic paper in relation to the
,~ r 22
filters and illuminant source, the corresponding exposure
times to substantially reproduce each target color on the
photographic paper were determined, with reference to the color
reference data base, to be:
Exposure Exposure Exposure Exposure
of yellow of magenta of cyan of black
separation separation separation separation
film film film film
Filters
25 (red) 0.2 sec. none 103.7 85.7
58 (green) none 53.0 5.9 52.6
47B ~blue) 36.3 19.0 4.2 46.1
To extend the exposure times for improved control
thereof in a manner known per se, each filt~r pack had included
therewith a neutral density filter of 1.50 rating, to reduce
the intensity of the light from the illuminant source, and
also an ultraviolet absorbing filter, utilizing filters for
these purposes which are commercially available from Eastman
Kodak Company.
The photographic paper was exposed to the illuminant
source successively through each filter for each of the in-
dicated times for each separation film in succession.
Exposure times were controlled semi-automatically by a DIT
200 (trade mark) timer, marketed by Sergeant-Welch Company.
With the photographic paper thus exposed, it was then,developed
in the conventional manner, according to manufacturer's
specifications. The exposure and development cycle was
completed in about fifteen minutes, and can be even faster
if neutral density filters are reduced or not used. Upon
, -23-
~73L~3~
drying, the developed photographic paper provided an
accurate color proof o~ the proposed prin-tiny run based
on the color sep~ra-tion negatives at hand, using the
selected inks and prin-ted on the type of paper presen-ted.
FIG. 2 diagrammatically shows the overall color
printing reproduction procedure utilizing the color
proofing technique shown and discussed in connection with
FIG. 1. Proceeding from a color original of either a two
dimensional or three dimensional nature, four color
separation films are prepared in a manner conventional
per se, such as by photography. As known, these separation
films can be either positives or negatives and of a screened
or half or continuous tone character. The color separation
films may then either go directly to a printer who does
his own color proofing, or to a specialty color proofing
shop where the color proof is prepared for subsequent
approval and delivery to a printing house. Given a set of
color separation films and certain candidate inks and paper
or like base on which the color reproduction is to be
printed, the printer or color proofer prepares swatches
of the inks on the printing base or reasonable facsimile
thereof and then proceeds with the production of one or
more color proofs, following the procedure illustrated and
discussed in connection with FIG. 1. The resulting proof
or proofs are then inspected and approved by the printing
buyer, such as an advertisiny agency or the like. Prin,ting
plates in the respective colors are then prepared from the
respective color separation films in a manner conventional
per se, such as by known etching processes, and the resulting
printing plates are utilized along with the respective selected
inks and the selected paper or like printing base during the
printing run, also in the manner conventional per se.
24-
8~3
In utilizing this color proofing technique, it will
be readily understood that it is applicable to a wide
variety of color proofing needs, such as in the reproduction
of original works or art or other art work, colored signs,
sample variations for textiles, wallpaper variations, .
paint or color swatches, variations in rug pattern colors,
plastics, or anything requiring a visual sample or samples
of what a finished product might look like in color.
Reproducing colors of natural products such as fruits or
vegetables, or a glass of wine, for example, is also an
application of the present technique, where the color
components of the natural product can be measured with a
spectrophotometer and the colors reproduced on photographic
paper by the target color reproduction technique of the
present invention, then reproduced rom given inks as a
printed color reproduction, with the colors of the printed
reproduction when printed being "proofed" in relation to
selected inks by the color proofing technique of the present
invention.
Various modifications, further adaptations and
variations will readily occur to those skilled in the arts
to which the invention is addressed. Thus, simply by way
of further example, it will be recognized that other coloring
agents, such as pigments or dyes rather than printer's
inks, may be equally well addressed by the target
color reproduction technique of the present invention,
and that the nature of the base to which the inks
or the like (e.g. pigments or dyes) are to be applied
may be readily varied. Thus, the particular nature
of the printing paper (matte or glossy, for example),
~h ~ 25
~7~3B
L otiler teXtlll^(.' oE the pr.int base (whicl~ Inay ~e three d:imell-
sional sucll as cquipment fronts or calculator keys or the
like), can wiclel.y vary in praet:i.ce alld ean }~e readi].y matehed
or at least closely simulated in practice of this color
proofing technique.
In util:izi.llcJ the present invention, it is an importan-t
advantacJe and characterlstie that the determination of the target
eolor color consti-tuents ean take into aecount the color of the
paper or other printing base itself, which of course contributes
its eolors -to the eolors of the ink or the like swatches.
Rather than requiring any partieular co~or proofing Eilms
and any partieular type oE film or paper on whieh the eolor proof
is to be developed, the color proofing teehnique of the present
inven-tion may be used with any photosensitive pho-tographie
paper oE any texture, it being reeognized o:E course tha-t un-
developed photographic paper is commercially available or
ean be made -to order in a wide variety of eolors, -textures
and confi.gura-tions and is a eonsiderably more eeonomie eon-
sumable than the speeially prepared photopolymerie materials
heretofore required for pre-press eo:Lor proofincJ.
Tlle eolor proofing teehnique of the present invention,
by means of whieh ~ color proof is ob-tained by suecessive
exposure of undeveloped photographic paper to an illuminant
light source through color separation films suceessively
plaeed in register on the photographie paper and through
sueeessive eolor filters for sueeessive exposure times
ealculated to substantially reproduee eaeh eolor assoeiated
with each color separation film on the photographic paper
when developed, is not neeessarily limi-ted to any partieular
teehnique for determining the eolor or eolor eomponent makeup
of -the ink or -the like with whieh eaeh eolor separation film
-26-
- ~4~ 38
is correlated. ~l`hus, in a given instance, the correlation
between a given ink or the like and a given color separa-tion
film, in terms o:E the filters and exposure times necessary
to substantially reproduce the ink color on a particular
~5 g.iven photograpllic paper or the li.ke, may be determined as
a factory specification or be otherwise available to -the
color proofer. 1t is con-templated, Eor e~ample, that a
manufacturer and ma-terials supplier to -the color proofing and
printing trade can provide the -trade wi-th a color prooEing
"package" involvinc3 an inventory of printer's i.nks or the like,
an inventory of colored filters and illuminant source or
sources, an inventory of types of undeveloped photosensitive
photographic paper, and a computer or l:ike equipment pre-programmed
to correlate any particular ink and any par-ticular paper with -the
available illuminant source~s) and color fil-ters, and provide
the appropriate corresponding filter exposure -times, such
computing or like equipment as furnished by the manufacturer
proviclincJ to tl~e color proo:eer a direct readout o:E the
photographic paper -to be used and the illuminant source,
filters, and associated exposure times to be used in -the
given instance. It is further contempla-ted tha-t, with -these
outputs, such an equipment could be automated in the sense
that exposure of the paper through each color separa-tion
film and its associated group of filters would be auto-
matically controlled by the equipment. At the beginningof a run -the color proofer manually inputs to the equipment
the identity of the targe-t colors to be reproduced (e.g.
the printer's inks or the like to be used during the
prin-ting run), the nature of the paper -to be used during
3~ the printing run, and possibly any corrective inputs
~7~38
des:irc(l .s~lcll al modi.ficati.orls in huc or tonc. 'l'he pre-
programmecl equi~ lent would then autornatica:Lly determine
the illumi.nant sou~ce, the group oE fil.ters and exposure
times to bc usecl to :reprocluce the color oE each given ink
or the like, and on demand would automatically sequence
the filter exposures through each separation fi].m. Operation
of the eqlli.pmellt would involve the color proofer simply
sequential.ly regi.stering the first col.or separation Eilm
with the photograpllic paper, then activating the equipmen-t
to perform the filter exposure sequence associa-ted with
the ink correlatecl with tha-t separation film, -then re~oving
the first separation film fxom -the paper and registering
the second separation film therewith, then again ac-tivating
the equipment to perform -the associated filter exposure
sequence for the ink correlated with the second Eilm, and
so on until the paper is fully exposed through all separation
films and associa-ted filters. Following the exposure cycles,
then, such equipment could also be automated to automatical.ly
develop the photographic paper and deliver -the developed
photographic media to the color proofer as the finis}led
color proof.
From the foregoing, various further applications,
modifications and adaptations of the method disclosed by
the foregoing preferred embodiments of the present invention
will be apparent to those skilled in the art to which the
present invention is addressed, wi-thin the scope of the
following claims.
-28-
