US3576627A

US3576627A - Process for the production of a photographic copy which simulates a multicolor print

Info

Publication number: US3576627A
Application number: US856152A
Authority: US
Inventors: Kuno Wirth
Original assignee: Ciba AG
Current assignee: BASF Schweiz AG
Priority date: 1968-09-12
Filing date: 1969-09-08
Publication date: 1971-04-27
Anticipated expiration: 1988-04-27
Also published as: NL6913872A; CH501250A; DE1942682A1; BE738755A; FR2017876A1; GB1267823A

Abstract

A PROCESS FOR COPYING COLORED IMAGES FOR THE PRODUCTION OF PHOTOGRAPHIC COLORED POSITIVE IMAGES FOR SURFACEVIEWING IS PROVIDED. THIS PROCESS, ALSO CALLED COLOR PROOFING ALLOWS RAPID RECOGNITION OF THE MATCHING WHICH THE FINAL PRINTED PRODUCT WILL SHOW IN THE PRINTING INDUSTRY, ESPECIALLY IN THE MANUFACTURE OF MULTI-COLOR INTAGLIO-PRINTED PRODUCTS. IN THIS PROCESS THE POSITIVE COMPONENT COLOR SEPARATIONS AND THE BLACK SEPARATIONS OF THE ORIGINAL ARE PROJECTED ONTO A LIGHT-SENSITIVE POSITIVELY ACTING COLORPHOTOGRAPHIC MATERIAL CONTAINING SILVER HALIDE. THE BLACK SEPARATIONS ARE NOT USED DURING THE WHOLE TIME OF EXPOSURE. THE AMOUNT OF LIGHT OF THE EXPOSURE OF A COLOR SEPARATION WITHOUT AND WITH THE BLACK SEPARATION IS IN A RATIO OF 1:19 TO 1:1.

Description

. PROCESS FOR THE United States Patent '0" 3,576,627 PRODUCTION OF A PHOTO- GRAPHIC COPY WHICH SIMULATES A MULTI- COLOR PRINT Kuno Wirth, Marly-le-Grand, Switzerland, assignor to Ciba Limited, Basel, Switzerland No Drawing. Filed Sept. 8, 1969, Ser. No. 856,152 Claims priority, application Switzerland, Sept. 12, 1968,

, 13,674/68 Int. Cl. G03c 5/08; G031? 3/10 US. Cl. 9623 5 Claims ABSTRACT OF THE DISCLOSURE A process for copying colored images for the production of photographic colored positive images for surfaceviewing is provided. This process, also called color proofing, allows rapid recognition of the matching which the final printed product will show in the printing industry, especially in the manufacture of multi-color intaglio-printed products. In this process the positive component color separations and the black separations of the original are projected onto a light-sensitive positively acting colorphotographic material containing silver halide. The black separations are not used during the whole time of exposure. The amount of light of the exposure of a color separation without and with the black separation is in a ratio of 1:19 to 1:1.

The present invention relates to a process for copying coloured images for the production of photographic coloured positive images for surface-viewing which in the printing industry allow rapid recognition of the matching which the final printed product will show.

Such a rapid process has for a long time been shown to be necessary in the intaglio printing industry in order to guide the retoucher and in order to be able to take into account special customer wishes at an early stage of the printing process. The need to subject the finished con1 ponent print positives to a control in respect of the correctness of their colour value before the printing rollers are etched is of long standing.

There has been no shortage of attempts to develop such a process (colour proofing) but the hitherto existing processes have either proved too complicated or too expensive or lead printed product. Thus all processes which employ transparent films are complicated and unreliable in their results. This applies both to the films which are placed one upon another and as a result of many reflecting surfaces differ from the photomechanical printed product and also to the processes in which the individual layers are detached from the layer supports and glued together in register with great difliculty. I

Particular problems occur in four-colour intaglio printing where apart from the three colour separations a black separation is also used in order to produce additionally the grey and black shades in a fourth passage with black printing ink. Difiiculties arise because when a photographic material is used for the manufacture of so-called colour proofs, the black separation cannot be copied by itself following the three colour separations since in contrast to printing in the case of positively acting colourphotographic material the colour densities are degraded to results which are too unlike the final Patented Apr. 27, 1971 ice 7 through exposure to light and the maximum densities are thus only achieved where no exposure whatsoever to light has taken place. This difiiculty can be circumvented by always copying the blackseparation together with the three colour separations. The black separation contains information from all three colour separations so that when it is used together with these colour separations this information remains preserved.

This method is however unsatisfactory in many respects. In some cases for example the black separation proves to be too intense for photographic use so that a loss of detail in the shadow portions and a blackening of the medium shades can occur.

A process has now been developed which does not have all these disadvantages and which leads to images which very closely approach the intaglio-printed product, espeprojected with light onto a light-sensitive positively working colour-photographic material containing silver halide, wherein the component colour separations corresponding to the individual colours are successively projected onto the light-sensitive colour-photographic material using the light of the corresponding colour, in each case once without and once together with the black separation, the amount of light in the exposure with and without the black separation being in a ratio of 1:19 to 1:1, preferably 1:9 to 1:1, and the exposed material is developed to give a positive image for surface-viewing. The process according to the invention is primarily suitable for simulating multi-colour intaglio-printed products.

Photographic material for the silver dye bleaching process has proved particularly advantageous for the process according to the invention, since colour images can be produced therewith in which the colours correspond relatively well with the printing inks in colorimetric respects.

A further advantage'of the photographic material for the silver dye bleaching process consists of the fact that positive copies of positive separations can easily be produced therewith. The present process is however not restricted to photographic material for the silver dye bleaching process and material which is for example used for the colour development process is also suitable, even if less successfully.

A suitable colour-photographic copying material for the silver dye bleaching process advantageously has a silver halide emulsion layer on an opaque support, sensitised to red light and dyed with a bleachable cyan dyestuff; a silver halide emulsion layer sensitised to green light and dyed with a bleachable magenta dyestuff; optionally, a

3 Y particular describe suitable magenta dyestuffs and British patent specifications 1,042,300; 969,146 and-'1-',03 9,458 in particular describe suitable cyan dyestuifs.

The component 'colour separations required for the process according to the invention, for example a green, red and blue filter separation, and the black separation are produced in the usual and known manner. Since these component separations are in the form of monochrome and indeed generally black and white images, one only remains dependent on the spectral sensitivities of the copying material in choosing the copying lights for the further photographic processing. I i

The component colour separation positives, which are thus mostly black and white, in other respects correspond ,to the continuous positives used in the half-tone intaglio printing technique. As a rule these positives are contact copies or enlargements of separation negatives which have been produced by means of colour filters, either conven- .tionally or via. a so-called scanner. The contrast range, that is to say the difierence between maximum and minimum density, of the colour separation positives, is as a rule adapted to the requirements of the individual printing works and is generally within the limits of 1.2 and 1.7.

v Preferably not all colour separations are of zero density at the same points.

Apart from the colour separations which are as a .rule three in number, a black separation is also produced so as to improve the reproduction of the neutral grey a'fid 'black. Instead of a black separation, reference is also frequently made to the separation of the light and dark 4 contrasts or to the so-called black plate. The density and ,character of the black separation also vary from factory I to factory.-Depending on requirements, the black positive is for example produced as a skeleton of relatively high contrast or as a half-tone copy with good depiction in the middle shades. The total proportion of the printed maximum density attributable to the black separation also dilfers. As a rule it is between and 30%, but can incliease up to 100% using special techniques in grey and b ack.

Thus, the process according to the invention is carried out in such a manner that, depending on the density and range of the black separation, the latter is co-exposed to a greater or lesser extent together with the colour separations, this being done in such a way that the proportion of the exposure of the black separation together with the colour separation amounts to 50 to 90% of the total exposure. A total of 6 component exposures is thus dealt with, proportion of the exposure together with the black separation relative to the total exposure being capable of variation within the specified liimts, depending on the subject and on the image character.

Represented schematically, the sub-division of the exposure for example looks as follows:

total 'oluc co.' we: blue rilzcr ive clack separation exposure cozpo'nent exposure green filter positive total green total 4. component exposure eposne green filter positive exposure clack separation 5. component exposure an 11.1: o ,1-1ve total red 6. component exposure exposure 7 red filter positive black separation The blue filter positive is copied with blue light into the blue-sensitive emulsion, the green filter positive with green light into the green-sensitive emulsion and the red filter positive with redlight into the red-sensitive emulsion-At the same time the sequence of these exposures can be interchanged. If the necessary optical equipment is available, several of these exposures can also take place simultaneo'usly. Furthermore, the copying light in each case does not have to be monochromatic in the strict sense. This is because particularly good images resembling the mechanically printed product'are obtained when the light used extends into regions where the sensitizations of the individual layers overlap, or when the separations are copied with certain proportions of wrong light.

The so-called black component does not haveto be the same for all three colour exposures. In some cases better results are obtained when twoor three diifer'entblack components are used.

The light-sensitive positively working colour-photographic material containing silver halide which has been exposed in accordance with the process of the invention may be developedin a usual and known manner. In the case of the preferred use of photographic material for the silver dye bleaching process the silver is first developed, the dyestulfs are then bleached in the areas where there is metallic silver, and finally the excess silveris removed. However, a colour image is obtainedin all cases which comes close to the mechanically printed product which can be obtained from the same separation positives. These colour images are used in the printing industry for pro-' ducing so-called lay outs and maquettes and as colour proofs. Here it must be noted that the "colour proofs manufactured according to the invention in mostca'ses however, are not completely able to replace the so-called pull in printing works. With the aid of the photographic colour image the expert can however makethe requisite changes in the separation positives before-'tlie'printing cylinders have been etched. When the colour :iniag'e's'are satisfactory, the separations-are released forprinting'or forthepull.-- I It can be seen from the examples whichfollow'that there is no strict connectionbetween the density range of the separation positives and the black component which is to be used for the manufacture of the photographic copy which simulates the multi-colour print. As a rule it can be said that a black separation of low density range requires a higher black component when producingthe colour copy. Circumstances can, particularly in cases of wide differences between the colours, be such .that this general rule is no longer valid. Since however, every printing works uses a very particular separation characteristics, the correct black component in the colour copy must once be empirically determined with accuracy. The exposure ratios thus determined are then valid for the particular works as long as the character of the colour separations is not changed.

Another way of determining the correct black component consists of first setting up so-called nomograms. Insofar as the density range of the black separation and of the individual colour separations is then known, the exposure component of the black separation in combination with the colour separation can be read off from-the nomogram. A particular nomogram is always only .pre-

'cisely valid for a particular'material with a particular exposure range and for a very particular processing. procedure. Mathematically, the exposure component of -the blackcolour separation combination can be calculated as follows: V

10- -10- 10. F-' 1-1o s wherein:

x=exposure component of the black separation and colour separation combination in percent, v

D =density iiange of the colour separation,

D =density range of the black separation,

D =exposure range of the photographic material;

For the axes of the nomogram, A-axis=density range of the black separation,

.B-axis=density range of the colour separation,

C-axis=proportion of the exposure time for the blackcolour separation combination,

The nomogram however only provides exact data for black separations with a rectilinear shade variation. The following examples illustrate the invention.

EXAMPLE 1 The separation positives of a coloured original image are copied in the following manner onto a photographic material for the silver dye bleaching process which contains a red-sensitised, green-sensitised and blue-sensitised layer: a

The blue separation B- is combined with the black separation S and projected through a blue filter. The black separation is then removed and the blue separation by itself is again projected. The exposure times are so chosen that the two exposures B-l-S and 3 give the correct density scale and shade value scale on the photographic material. The same procedure is repeated with the green separation and the red separation, using the corresponding green and red filters respectively.

The various exposure times and the density range AD of the individual separations are summarised in the table which follows:

6 EXAMPLE 3 Separation positives of an original colour image are copied onto a photographic material for the silver dye bleaching process in the same way as described in Example l.

Total exposure AD time, secs. Component exposure times Separation:

B 1.46 10.4 B=2.6secs B+S=7.8secs.=75%.

26 G=6.5 secs G+S=19.5 secs.=75%. 20 R=5.0 sees R+S=15.0 secs.=75%.

The empirically determined black component is thus 75%. The colour copy thus obtained comes very close to the printed products made with the same separations, particularly as regards the neutral grey shades produced by the three colour separations.

EXAMPLE 4 Total exposure AD time, secs. Component exposure times 1.43 9. 1 B=1.3 secs.. B+S=7.8 sees.=86%. 1. 17 11. 5 G=L6 secs.... G+S=9.9 secs.=86%. l). 10. 5 R=1.5 secs R+S =9.0 secs.=86%.

The separation positives of an original colour image are copied onto a photographic material for the silver dye bleaching process in the same manner as described in Example 1.

Total exposure AD time, secs. Component exposure times 1.36 6 3:2 secs B+S=4 secs.=67%. G 1.40 12 G=4 secs G+S=8secs.=67%. 1.42 10.5 R=3.5 sees R-l-S=7secs.=67%.

The empirically determined black component is thus 67%. The colour copy thus obtained comes very close to the printed products made with the same separations, especially as regards the neutral grey shades produced by the three colour separations.

Total exposure AD time, secs. Component exposure times Separation:

B 1. 41 5. 2 B=0.8 secs B+S=4.4 secs.=%.

. 26 11. 8 G=1.3 sees G+S=10.5 secs.=89%.

8.4 R=1.8 secs R+S=6.6 secs.=79%.

In the present example, the black component is not the same in all three colour exposures because in order to achieve better results it is often advantageous to use two or three diiferent black components. The empirically determined black components are here 85%, 89% and 79%. The colour copy thus obtained comes very close to the printed product obtained with the same separations, particularly as regards the neutral grey shades produced by the three colour separations.

EXAMPLE 5 Separation positives of an original colour image are copied onto a positively working photographic material for the silver dye bleaching process in the same way as described in Example 1.

Exposure times in seconds B-l-S, AD Total B percent The black component was determined as 85% for the blue separation with the aid of the nomogram given hereafter. For computing the nomogram, 1.6 was used as the intended value for the exposure range of the photographic material for the silver dye bleaching process which was employed. The value of 85 for the black component which was determined in this way was for simplicity also used for the green and red separation.

In the nomogram the symbols denote:

A=Axis for the density range of the black separation B=Axis for the density range of the color separation C=Proportion of the exposure time for black-colour separation combination in percent.

The colour copy thus obtained comes very close to the printed product made with the same separations, especially as regards the neutral grey shades produced by the three colour separations.

EXAMPLE 6 Separation positives of an original colour image were copied onto a positively working photographic material for the silver dye bleaching process in the same way as described in Example 1.

Exposure times in seconds B-l-S, AD Total percent Separation:

EXAMPLE 7 Separation positives of an original colour image are copied onto a positively working photographic material for the chromogenic colour development process in the same way as described in Example 1.

Exposure times in secon s B+S, AD Total percent Separation:

The black component was determined as 85% for the blue separation with the aid of the same nomogram as specified in Example 5, and was for simplicity also used for the red and green separation.

The colour copy thus obtained comes close to the printed product made with the same separations.

NOMOGRAM t. so 1,4

What is claimed is:

1. A process for the production of a photographic copy which simulates a multi-colour print in which the positive component colour separations and the positive black separation of the original are projected onto a light' sensitive positively acting colour-photographic material containing silver halide, wherein the component colour separations corresponding to the individual colours are projected successively onto the light-sensitive colour-photographic material using the light of the corresponding colour, in each case once without and once together with the black separation, the amount of light of the exposure without and together With the black separation being in a ratio of 1:19 to 1:1, and the exposed material is developed to give a positive image for surface viewing.

2. A process as claimed in claim 1, wherein the amount of light of the exposure without and together with the back separation is in a ratio of 1:9 to 1:1.

3. A process as claimed in claim 1, wherein a photographic material for the silver dye bleaching process is used as the colour-photographic material.

4. A process as claimed in claim 1, wherein a multicolour intaglio-printed product is simulated by the photographic copy.

5. A process as claimed in claim 1, wherein depending on the density and range of the black separation, the latter is co-exposed together with the colour separations so that the proportion of the exposure of the black separation together with the colour separation amounts to 50 to of the total exposure.

References Cited UNITED STATES PATENTS 3,215,030 11/1965 Jordan 96-23X NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner U.S. Cl. X.R. 96-35