Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED COLOUR REPRODU_ r_ ON PRO ES,S
This invention relates generally to the printing
industry, and has to do particularly with a process for
the generation of the plates necessary to permit colour
printing, Even more particularly, the present invent:ion
sets forth a method of reducing the number of individual
plates which need to be made to satisfactorily reproduce
a given coloured picture, painting, transparency or the
like,
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BACKGROUND OF THIS INVENTION
Currently, a process known as the four-colour
separation process lS very widely used in the printed
reproduction of coloured pictures, transparencies and
the like. The four-colour separation proeess is
generally responsible for all of the high-quality
coloured reproductions in magazines and books, and is
also used for some newspaper work as well, ~ -
In diseussing the four-eoIour separation proeess,
prior art textbooks have often used impreeise and
sometimes eonflieting terminology in describing the
colours of proeess eomponents. For example, Donald E.
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Cooke in his book "Dramatic Colour by Overprinting",
first published in 1955, second revised edition 1974,
the autllor speaks of process or lemon yellow, process
red or magenta, and process blue. In t1escribin~ an
example colour reproduction at pa~e 74H, the two-colour
reproduction is described as using magenta and process
blue on yellow base, but in the text below the
reproduction is said to be using only two colours,
magenta and blue, printed on a yel10w base, For an
accurate description of the colours involved in -the
process of colour separation and colour printing
reference is given to John E.~ Cogoli's book "Photo-
offset Fundamentals", published~1973 by MacKnight
Publishing Company, where a full explanation of colour
reproduction~is given in Chapter 10, Accordingly, there
are three additlve primary colours blue, red and green,
Each of the additive primary colours has its
complemen~tary colours; yellow is complementary to blue,
cyan is complementary to red and magenta is
;20 complementary to green. Because of their appearance,
cyan and magenta have often inaccurately been termed
process blue and process re~d; even more inaccurately
cyan has been~simply termed blue. It xhould be noted
that process red and process blue refer -to two
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transparent printing inks among the ~our process inks
utilized in the colour printing process,
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In the most common version Oe the four-colollr
sepàration process, the original colour print or
transparency is photographed through difEerent filters
or scanned by an automatic scanrler as illustrated on
page l90 of the textbook by Cogoli above mentioned; to
produce di~ferent individual filrns which correspond to
the basic colours of the four-colour separation process:
yellow~ ma~enta or process red, cyan or process blue and
black. Because the films produced are separation
negatives, the filters utilized to draw out these
colours from the original havé tints which are the
complementary colours of the cDlours being drawn out.
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rhus, a green filter is used to pick out the magenta or
process red. a red filter is used to pick out the cyan
or process blue, and a blue filter is used to pick out
the yellow. A combination of all filters is ideally
utilized to pick out the skeleton black, although in
some processes t~he black film is made by photographing
.
the original in black-and-white film, without any
filter.
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Some "fine tuning" or adjustment of the in~ensities
of the various colours in the process is made by
selecting exposure times and development times. Also,
in some instances the final inks used to print the fina]
reproduction can be varied and selected to atta:in
certain effects.
From the four pieces of film produced through th:is
process, printing plates are ~lade, these bein~
subsequently attached to plate cylinder in a typical
printing machine, which is then able to print thé
reproduction.
Generally speaking, the printing industry is of the
view that proper reproduction of any photograph or the
like requires a our-colour separation process of the
kind just described,
However, in certain branches of the printing
industry t par:iculsrly in newspapers, shopping bags, the
YelIow Pages and advertising flyers, the full four-
colour separation process represents a considerable
expense, sinee it requires the material to be passed
through four;printing stations, in order to receive the
* Trade Mark
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~our colou~-s. This in turn requires the production of
four plates, and the time required to mount thern, adjnst
the cooponents, etc, All of this represents a
substantial cost factor which, for obvious reasons, it
would be o~ advantage to reduce.
There is a two-ink process Eorming part of the
prior art, known as duotone. In one version of this
process, often called "Fake" duotone, a black and white
original (for example a photograph) is first
photographed on "Ortho" film through a contact screen to
give a screen negative. "Ortho" film is a high contrast
film which is not sensitive to the red region of the
spectrumO Then, the same screen is rotated through 30
and another screen negative is taken, substantially
identical to the first, also on "Ortho" film. The two
films are developed to different densities, then are
used ~to make plates which are run in tao colours, for
example, red and black.
In another version of duotone, often called "Real"
duotone, the original art is already ïn two colours, for
example, red and black. The first step is to shoot
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"Ortho" film throu~h a grey contac-t screen without any
filter. Both the red and the black will be seen by the
film, and the result will be a film in which the red and
the black are both picked up as black for printing in
red. Then, a panchromatic film is e.~posed through a red
filter and a grey contact screen. In this arrangement,
the film sees only black for printing in black.
The two films, which are negatives, are then used
- to make plates which print red and black, respectively.
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It is also known, particularly, in the food
advertising area where blue colours are rare, to do a
three-colour separation using the standard filters to
obtain yellow, magenta or process red and cyan or
process blue, and then to print the image using yellow
lS ink, red ink and black ink. In other words, the plate
mad2 from the cyan or process "blue" film prints in
black ink.
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It is further known to mix various colours to
produce various other colours, For example, it is known
to print a dot matrix of black superimposed on a dot
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green. It is also known that rnagenta or process red and
yellow will combine in the same way to produce orange.
It is further known that yellow and cyan or process blue
- will combine to produce various shades of green.
I have now discovered and developed a process for
production of separation negatives and printing pla-tes
by which to attain strikingly realistic reproduc~ions of
an original utilizing only two printing plates inked
~ with only two different non-process colours. Ilowever,
; ~ 10 the process of making these plates does not involve
simply one of the known parts of the standard four-
colour separation.
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~;~ By way of explaining this, it should be understood
~- that, if a four-colour separation were made to produce
~ 15 four plates intended to print yellow, magenta or process
'-- red, cyan or process blue and black, and then if only
~ the yellow and magenta or process red were printed, or
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only the yellow~ ~cyan process blue and black, or an
- other combination which was not the full combination of
four colours, the resulting prlnt wouid be clearly and
definitely unbalanced, and anyone viewing the print
~` would immediately see -the unbalanced nature of the
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colours. The print would appear "too reddisll" or "too
far into the blue region", or blotchy. The aim of the
process which I have developed is to remove the
unbalanced nature of a printed reproduction ma~e with
only two impressions, and thus two inks,
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GENERAL DESCRIPTION OF TIII.S_INV_NTION
Simply stated, the improvement which I have
developed consists in utilizing, for at least one of the
two plates~ a combination of two or more of the standard
filters utilized in a typical four-colour process. As
is ~ell kno~n in the prior art, for example by reference
to the above mentioned book by Cogoli, combining two of
the standard filters, when performed on a scanner, is
accomplished electronically by computin~ from colour
information obtained by scanning -the original image aND
analyzing its colour content using the same standard
filters. Such computation is similar to that performed
~- for purposes of colour correction as mentioned by Cogoli
; on page 189.
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More particularly, this invention provides a method
of printing on a sheet member a realistic image of an
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original, utilizing two di~ferent superimposed
impressions with two different colouring media. The
method includes creating a first prin~ing plate by the
interposition of at least two filters between the
ori~inal and means for recording a first optical image,
then creating a second printing plate by the
interposition of at least one filter between the
origi.nal and means for recording a second optical image.
Then, the first and second plates are used to print the
different impressions with two different colouring
media.
ln a preferred embodiment, the means for recording
the first and second optical images are pieces of
photographic film, and t:le colouring media are non-
process printing inks.
In another embodiment, the invention provides amethod of preparing a colour separation negative film,
for exposing a printing plate for printing a partial
printed image of a colour bearing original image with a
predeter~ined non-process ink, comprising the steps of:
(a) creating on said separation negative film a first
image exhibit~ng a first range of~densities
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corresponding to a predetermined sin~;le colour component
in said original image; and (b) crea-tin~ on said
separation negative film a second irnage exhibiting a
second range of densities corresponding to another
single colour component in said original image, whereby
two such printing plates, when used to print two
superposed impressions with two non~process inks of
different colour, print an improved printed image,
In still another embodiment, the inven-tion provi.des
a method of printing on a sheet member a printed image
o:E a colour bearing original image, utilizing two
different superposed partial printed images each printed
with one or two predetermined non-process ink,
comprising: (a~ creating a first printing plate bearing
printing information corresponding to at least two
colour components in said original image; (b) creating a
second printing plate bearing printing information
corresponding to at least one other colour component in
said original image; and (c) using the first and second
printing plates to print the superposed partial printed
images each with a different one of the two
predetermined non~process inks.
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DETAILED D~scRlprrlo~-oF THIS I~VE~TION
This invention will first be described as it
relates to the printing 1ndustry, and subsequently as :it
relates to the copying industry.
In one embodiment, when used in the photographic
reproduction area, the method of this invention involves
making two films by exposure to the originalj at least
one of the films being made by the interposition of a~
least two filters between the original and the film
during exposure. The filters are used sequentially,
rather than together at the same time, Tlle second film
may be made in the normal way to select out another
,
colour, utilizing o~nly a single filter. In a more
-~ complex version, the second film may also be the result
of utilizing two filters sequentially,
As an example, consider the problem of printing~a
picture of a baby;'s face with blue eyes against a light
; blue background.~
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Let us assume ~hat the first film to be made will
be that for the plate intended to print red ink. In
order to pick out the red tints, a green filter i.5 first
utilized, and this produces a first exposure on the
film. Then, in accordance with this invention, a second
filter would be utilized. In this example, I would
typically utilize a blue fllter to draw out some of the
blue~ for example the blue eyes of the baby, by
excluding some of the red that is to be printed by this
first plate from the eyes of the baby. This would also
pick up some of the blue background~ i.e. less red will
be printed there as well. However, for this filter I
would adjust the exposures so that the film contained
more of the red than the blue (meaning that in the
negative, exposure through the green filter is longer
and as a result the range of densities reaches high
values), in order to clean out the red tone in the blue
eyes, while still leaving enough to enhance the
contrast.
The second film would be -that intended to make a
plate for printing blue ink. In this example, the
"blue" film would be exposed only through a red fiIter,
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red being complementary to cyan ( which is a combinatior
o~ blue and green), so that not on]y blue irl the
original but also green, if any, would be printed as
blue.
Suppose now that the same picture of the baby
against a blue background were to be printed on yello~
stock, for example as a telephone advertisement in the
Yellow Pages. In this case, one o~ the two inlcs must be
black, since the normal "word" advertisements are
printed in black. Because the baby's face is
predominantely pink or flesh tone, the coloured ink
would be non-process red. However, instead oF merely
using a green filter, one would use first a green filter
to draw out the red tones, and then a blue filter to
"fill in" the blue regions, for example the baby's eyes
and the back~round by printin~ less red thereat. The
blue contribution would be considerably less than the
red. Nonethele6s, there would be some ink printed where
the original showed blue (the eyes and the background),
~; 20 and therefore the final printed image would be one in
which all major components were present. The second
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film (lntended to pr~nt black) ~ould be exposed throogh
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a r~d ~llter~ to plc~ up the hlue~ ,lnd the ~)lue eyes an(l
back~[)und~ so that the addition of black dn~,s ~o the
blue areils will ,,lve ~t ihe detall and Lesolu~ion
required~
l'his can be compa~ed to an atteml)t to print the
sa~.-.e pictuJe of d blue-eyed ~ by against a blue
back~round usino only the black and proce~s led or
mac,enta films fro~n a stanllald Fonr-colour sepafation,
In this lnstaYIce~ the result would be a Elat picl.ure
with 1nsufficiellt contrast,
In regard to the copyino industry~ -it is well
understood that the copying process involves the
esTablishment of a latent electrostatic inage on a dru,l:
or plate constituting a photocondllctive sulfclce,
following which a coloured "toner'` lS applied to the
i~.age-containing poltions of ti-e photoconductive
sur~ace~ the electrical attract1on causing the toner to
renlain in certain areas alld he relTloved from others,
following which the photoconductive surface with the
: 20 coner is ~pplled agains-t a sheet of paper which picks up
: the toner as an image. Copiers are known which are
capable oF colour reproduction. I'hese copiers wnrk on a
principle si~ilar to that util~zed in the four--co]our
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-~epara~ lon pr ocess df~scribed ear l:ier. I~ ne Lv l h.lt I hf'
photocollducti~e surtace is l~po~s~d t. h ~ f' e t l. r.' e S
se4ue(ltial1y to lh~ Ori~.Lrl J I, each t i :!1 e thro~,h .
differellt coloured filter. F`ollow~ L eacll exposllre to
t~s~,ll)l-ish the elec-rost.ltic image, a colonrell to~le~ Is
applied to the surface, ~In(~ the sheet is prl~ted with
that p,-lrticular colour, Therl the sllrface l~ c]ec-rled,
e~posed agL~ to the next filter, thell the next toner is
applied, and the same sheet is agaln prLnte{l with the
new colour, This colltinues for all three colours.
It ~ill be evident that the essence of this
invention can be applied to the copying industry, by
arrangin~ to have the photoconductive surface e~posed
through not olle but two (or nlore) filters. I'hese
filters ideally would be used sequentially to build up
an electrostatic image which is a composite of tile
images which would normally be obtained throllgh the two
difierent coloured filters. Then this connposite
electrostatic image is contacted by the appropriate
coloured toner, and the same is printed on the paper
sheet.
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Whl le one t~mbo(l-imellt ot I hi s invellt iOI~ has b~ erl
describe(l ~3bovr ~ i t w:i I 1 be evl.derlt to tho:j~ ski I le(l i"
(h~ art thclt chan~es all(l nlc)d:ilicatiol1s may t~c m~ade
therelrl withollt depdrtinj~, trom the es~jence oî this
invention, as set torth in the appen~lt~cl c:Laims.
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