PART II - CHAPTER I
THE COLOR ON GRAPHICS CHAIN

 

General

          What is the need of Color Management?

          A certain number of limits such as physical as well as economical slow down the development of color management. Each peripherals have a color space which is unique to them, and the purpose of the CMS or Color Management System is to control the transformations required between these different device of different color spaces and ensuring that color reproductions are connsistent. It creates profiles for each peripheral, and associates them with the peripheral for the purpose of making communications between different peripherals and better results in terms of colorimetric restoration.

          First, limits are observed with data from the peripherals. The ageing of the light source, the cleanliness of the mirrors used for reflexion, the CCD sensor and the phenomena which result from it, as well as the quality of the Analog to Digital converter (A.D.C) are four factors intervening directly in the operation of the color management for a particular peripheral.

          The limits observed on the level of the system of restoration (equivalent here to the monitor) comes from the various elements such as type of cathode ray tube (and its ageing) and the type of graphics card (standard of LUT used and type of Digital to Analog converter).

          The limits of the output are related to the fact that the color space of CMYK is more restricted than color space RGB(monitor). This is related to technology used to imprint(inkjet printer, sublimation, imaging film, offset printing etc). Qualities of inks used and paper also intervene in the result of the color management.

Currently, a system manages the color functions on a standard architecture, we will approach the principle characteristics of this sytem.



Diagram 15: Structure of a Color Management System




Diagram 16: CMS/Peripherals interaction
Difference between calibration and characterization.

          These two concepts are different, but are however completely dependent on each other. The characterization, also called shaping is a complementary stage of calibration, and applies for each device on the chain. The characterization connects the color perception of the peripheral with a colorimetric space. Calibration (either linearization or standardization) is an operation which calibrates a peripheral according to basic adjustments provided by the manufacturer of the hardware or according to characteristics fixed by a standard (gamma of the scanner, the white point, the black spot, the color temperature, gamma of the screen, the printer ink ). The two processes are same in their realization which generates a certain confusion to the users.

          Calibration intervenes on the behavior of the peripheral which is changed to obtain results close to those defined by the manufacturer.

          The characterization intervenes on a software level, without changing the behavior of the peripheral. Its role is to create a profile for each peripheral which could then be used by a Color Management System (CMS).



Diagram 17: Stages of the general principle of calibration


The creation of profiles
Calibration and characterization procedure
          The monitor calibration

          The calibration of the monitor is a preliminary phase in characterization, and it is essential since it is the peripheral on which the user makes his first judgements. Calibrating only one monitor is less tiresome than to calibrate several in the same way. With the Kleo range of products from Qubyx, it is possible to calibrate several monitors. The calibration of the monitor was being carried out in a visual way (ex: Adobe Gamma). This method is not suitable if there is more than one monitor to calibrate (the eye is a good comparator, but the observation differs according to individuals age, sex etc). It is thus not recommend using this procedure. Software calibration, using a sensor called colorimetre is regarded as most reliable and is being adapted more color management professionals. The use of a measuring apparatus is supposed to standardize the process, and to limit the drifts due to external factors.



Figure 11 : Qubyx Kleo software installation screen.

The calibration of the screen involves adjusting the luminosity, contrast, gamma and the color temperature of the white point. Gamma is the ratio which exists between the input of electric signal and the luminosity of the monitor. This value of gamma is different according to the data-processing platform used (MacOS or Windows). It is fixed at 1.8 for Macintosch and 2.2 for the PC. The ambient light must be controlled perfectly otherwise the quality of calibration will be non-optimal.

          Frequency of calibration

          In order to obtain constant colors on the chain, a regular calibration is strongly recommended. Thus, it is advised to carry out a calibration of the monitor every two weeks with at least one hour of heating of the apparatus. Kleo makes it possible to define this period in the Preferences window of the Calibration Frequency in the software. Thus, Kleo warns you automatically, when a calibration of the monitor is to be carried out. Also the frequency of calibration depends on the quality and stability of the monitor.


          The characterization

          The characterization of a monitor is carried out in a software way using a sensor(colorimeter). This procedure measures a series of neutral and coloured patches and then the software compares these measured data with those of reference data. Then it makes correction if it is necessary and a profile of the monitor is created which is stored in the Colorsync Profils folder.



Figure 12: A screen of Kleo35mm from Qubyx

The digitizer

          The characterization


          The use of a charter IT8.7/1 or IT8.7/2 is essential. It is necessary to calibrate the system in use(flat and drum scanners, digital film camera, digital video camera) by carrying out a calibration according to the source light type employed and according to the photographic film. In the case of a digital film camera, the source of light (ambient lighting) is continually changing. The calibration of a scanner is related with the adjustment of gamma.

          Software for creation of profile scanner exists at Qubyx, GretagMacBeth, Heidelberg, Colorblind. We can quote as example the software Kleo 35mm from Qubyx which makes it possible to characterize a scanner (in transmission and reflexion), by carrying out a profile for the peripheral. It also gives you possibilities of adjustment for the rendering intent, white point, black point etc.
In theory, software being used to create the profile, makes a comparison between RGB data resulting from the process of digitalization, and measures with LAB values of the charter (values of




Diagram 18: Principle of characterization of a scanner
reference provided by the manufacturer of the charter). Then It finds a correlation between the two and carries out the corrections if necessary.

Charters IT8

          Created by American National Standard Institute (A.N.S.I), via the collaboration of companies exerting in the fields of the Art-Graphs and photography, the purpose of charters IT8 is for the calibration and the characterization of the scanners. The various digitizers in the professional market varies according to the models and marks. This is partly due to the intrinsic properties of the scanners and films, namely the spectral sensitivity of the system of seizure and the variety of the dyes present in the emulsions (spectral densities of films and spectral concentrations of the dyes). The charters must thus provide the possibility to the scanner of adapting according to any type of dyes present in film. However, it should be noted that this test card is usable only for the colors slide films, and opaque documents.
Certain founisseurs of charters IT8 manufacture charters IT8 on various types of film (Agfa, Kodak, Fuji), thus allowing to create an ICC profile for each type of film.
It is also necessary to differentiate between charters IT8 delivered with a generic file of reference (obtained using an average of computed values. For example The GretagMacBeth Company,



In 1993, American National Standard Institute (ANSI) developed three standards related to graphic technology and charters IT8:
IT8.7/1-1993: Graphic Tecnology-Color Transmission target for input scanner calibration
IT8.7/2-1993: Graphic Technology-Color reflection target for input scanner calibration
IT8.7/3-1993: Graphic Technology-Input dated for characterization of 4-color process printing
It also exists of other charters which have the same goal to calibrate a peripheral, for example the charter ColorChecker DC from the company Gretag MacBeth.



delivers its charter ColorChecker DC, maybe with a file of reference obtained by average, or with several thousands of charters) and charters IT8 delivered with their own files of reference, whose each patch is measured individually with one spectropho with a measured file for this charter explicitly.



Diagram 19: Principle of characterization of a printer
Of course the price difference is important between the two, but for the professional use, it is recommended to use measured charter.

The printer

          Calibration

          The process of calibration is similar to that of the characterization, since it consists of printing a charter color test and to measure it in both cases of image. The purpose of the calibration of a printer is to control the density of inks and the rate of fattening and it guarantees a constant quality.
This calibration is carried out directly on the machine with impression, or with the RIP (Raster Image Processing). It is necessary to use a measuring instrument like densitometer, or spectrophotometer, as well as a ranges of control, offered by the FOGRA, the Brunner company or the manufacturer of the RIP.

          The characterization

The characterization of the processes of impression:

Contrary to that of the scanners and the monitors, the characterization of the processes of impression is much more complex. This is due to varied the possibilities of laying down the color on paper. To simplify, we will say that the processes of impression depend on the following parameters:
- procedure of impression
- paper used
- color of impression used
- covering of the color
Considering all the above parameters for the process of impression, it is thus impossible to characterize the printer or the press as an apparatus, .
The process of impression is different for different kind of papers. The process of impression has been described for each kind of paper. If the printer allows the adjustment of the color overlapping, this parameter must be taken into account at the time of the process of impression.


Ranges of control FOGRA


The FOGRA Bundesverband Druck E.V (Federal Union of German Graphic Industries, www.will fogra.org) developed two ranges of controls which is very useful for the color management called "Medienkeil CMYK" and "Medienkeil CIELAB".

The group of control CMYK is made up of two lines of beaches of color, divided into two groups. The first group carries initial A and B and the second group, initial K and G.
In more of these initial, each 34 beach of color of the first group is referenced by a number. In this group, one can finds the three primary colors cyan, magenta and yellow (tonal value of 100, 70 and 40%) as well as the mixed colours blue, red and green (each mixed colour being made up of 100, 70, and 40% of the primary colors, what is equivalent to a sum of tonal values of 200, 140 and 80%). In the two lines, beaches 10 to 17 includes a white paper and other 15 mixed colours which, with the impression, play a very important role in color space.
The group of the range of the gray contains the tonal values of the true patchs of gray. If K in the higher line indicates the beaches only made up of black (gray true), which means that the K03 beach corresponds to a tonal value of 3% of the color black. The line G includes beaches made up of the primary education colors Cyan, Magenta and Yellow (gray trichromatic). In the ideal case, a beach of the line G would present the same intensity and same colouring as the true gray of the line K.
The FOGRA took measurements, on various types of paper. These measurements are delivered in the form of value CIE with the range.




ATTENTION. Image has to replace by films for the imression.


          Printer RGB or CMYK:

          How to determine the type of printer used for the creation of the profiles.


The functionallity of systems of impression is in great majority with inks, toner, dyes or ribbons of four colors: cyan, magenta, yellow and black. This does not define the type of printer.
Indeed, even if the system of impression uses the CMYK, the management and computation software of the impression can work in RGB mode.
For the creation of the profiles, it is essential to know the type of your printer, RGB or CMYK.
For that, print standard file the " printer.tif " which finds on CD, without using particular



adjustment or of profile.
Then, on the printed result, look in the black rectangle.

Paper:

Categories of paper in the process of impression

The choice of the category of paper is one of the important factors in the process of impression. In practice, there are many categories of paper. for example art paper which has a very smooth surface intended for the quadrichromy. Non-art paper are of lower quality and are used in the photocopiers and laser printing. Newsprints are also named as non-art paper. However their quality is still well distinct of that of papers for photocopiers etc... In complement of this simple classification of the kinds of paper, comes to be added a more technical classification resting to measures according to standards FOGRA/BVD.

Index papers in various classes is also important as same CMYK values, printed on different papers, can give very different colors. In order to avoid the losses of quality, the values or films CMYK - once created - can be used only for one same kind of paper. The scans planned for higher art paper appears too much dark on non-art paper and drown in the dark ones.

Repercussion of the fattening and the maximum density of inking on the various categories of paper.

The factor of density with which the colors are printed associated with the quality of the paper on which the colors are printed.
On art paper, the color of impression forms an autonomous layer and reaches a maximum saturation. Non-art papers and more still newsprints absorb the color of impression. This is why primary colours cyan, magenta, yellow and black are less sharp.

The densitometer is used for the measurement of the density of colors CMYK. This instrument measures the reflection of the light of a surface. Before measurement, the instrument is gauged on the white paper. D=0 because the reflection = 100%. The values of density are calculated with the following formula: D = - logR where D=density and R = reflection.
A densitometer cannot indicate to you if a certain printed color corresponds to a Pantone color for example. A densitometer is able to measure a reflection and not a tonality of color.



According to paper, the color and adjustments on the machine with impression, maximum density is located roughly between D 0.9 (yellow on newsprint) and D 1.9 (black on higher art paper).


Increase in the cover of surface for each category of paper

In addition to the maximum density, the increase in the cover of surface is the second most important characteristic for a category of paper. The increase in the cover of surface indicates how much the cover rises on paper compared to film. For example a screen of 40% covers 40% of a surface with points of screen and leaves 60% free. At the time of an increase in the cover of surface of 16%, the tone of screen on paper occupies 56% of this surface and leaves some 44% free. Since more surface is covered by the color, the impression becomes darker. The increase in the cover of surface can be described in various ways. From an international point of view, the increase in cover is measured with a value of cover of surface of 50 %.


40% of cover on film (left) give at the time of an increase in cover of surface of 16% 56% of cover in impression (right).

Chart shows increase in values of tone for art papers compared to a curve without increase in values of tone.

To summarize we can say that more paper and the best densities of tone are good and can be printed more precisely and more the increase of cover of surface is weak. If one prints the same color on different papers, it occurs the following thing:

the art paper makes it possible to print the strongest colors but it can be printed with high densities of tone. On non-art paper, since the values of tone are low the colors appear softer . At the same time, the image is fuller because through more raised densities of tone, this is the reason the average and more sunk zones appear darker. On newsprint, the colors are softer and the dark sectors drown truly because of the very high density of tone.

As the digital image in CMYK can be printed differently on different papers, the preliminary stage with the impression tries to balance these variations as much as possible. Thus the intensity is already taken into account at the time of the digitalization and the separation of the colors adapted to various papers.In a Color Management System, only the profile of impression determines all the parameters of separation.

At the time of separation, the ratio of the black to the other three colors cyan, magenta and yellow play a decisive part. The same tone of Lab color can be returned different CMYK values on same paper .

When the cyan,the magenta and the yellow mix in a precise ratio in tone of neutral colors,




can made up of colors being replaced by black. When the cyan is replaced by magenta and yellow, the total quantity of color drops.

The against-offensive process consists of an addition of black in the dark and neutral sectors, in order to increase in contrast by a more constant black.This process is used for art papers which absorb hardly the color of impression and allow the best made total of the colors.
UCR GCR UCA
On non-art papers, ink penetrates into paper, this is why the sum of the colors is weak

 
  A chestnut made up of 80 % of cyan, 90 % of magenta and 60 % of yellow give a sum of color of 230 %   A chestnut made up of 77 % of magenta, 47 % of yellow and 62 % of black give to a sum of neck them of 186 %.

This process is ideal for non-art papers and the newspaper impression. As papers of this category strongly absorb the color of impression, it is necessary to act against the arrival of the dark zones of reason.
On art paper ink creates a layer. In order to get a maximum contrast quality of ink is important.  
  A pure black with a sum of color of 100 %.   A black made up of 45 % of cyan, 30 % of magenta, 30 % of yellow and 100 % of black give a sum of color of 205 %.



40 Cyan, 70 Magenta and 60 Yellow make a chestnut. There is at least 40% of each color. Since 40% Cyan, 40% Magenta and 40% Yellow from Gray, one can substitute C40,M40,J40 with 40% of black. The rate of fattening is 90% instead of 170 %. Or in the second case, one substitutes C20%,M20%,J20% by 20% of black. The rate of fattening is 130%.
When to begin substitution, and which level? You will find the rules in the GCR, UCR and UCA.



Cover of surface (rate of fattening) and composition of the black

The total returned colors is also called maximum cover of surface. One adds the cover then surfaces each color for the pattern of darkest sectors. The darkest tone in an image CMYK intended for newsprint in an impression with Offset roller has a cover surfaces of 230%.On art paper,it is possible to work with a cover surfaces of 370%, when the scans are optimized by a professional user so as to approach most possible pattern. Contrary to impression, there are not official directives for the standardization of the reproduction.


Basic terms around the composition of the black

By generation of black, one qualifies the method which calculates starting from Lab images, thus RGB the black layer at the time of the transformation into CMYK.

Short black and long black
The length of black indicates, in which sectors of clearness, the black replaces or supplements the colors cyan, magenta and yellow. Short black operates only in the dark sectors whereas a long black depend on the whole of the axis of clearness.

Narrow black and broad black
The width of the black describes with which intensity the black replaces the colors cyan, magenta and yellow in the saturated sectors. A narrow black replaces the values of colors CMY only in the neutral sectors by the black. Broad black also acts in the saturated colors.Using a broad black, it is possible to reach a maximum reduction of total colors returned. for example for the newspaper impression, there is the risk which the colors transfer with the gray, which can be negatively affect the tone close relations of those of the skin.

In practice, many professionals in reproduction prefer to work with a long and narrow black that gets a certain number of advantages in the reproduction and the impression.

Balance gray assured in impression
Even if intensities of tone for the cyan, the magenta and the yellow in the pulling impression vary slightly, the neutral tones in impression are surer with a long black sight than they are primarily made up starting from the black. Narrow black avoids a color transfer with the gray.

Use for all the categories of papers
As the cover of the highest surface is in the neutral and dark sectors, a long and narrow black can be carried out with different maximum covers of surface to coordinate it with all the categories of paper. For the very low covers of surface below 280%, the width of the black can be increased.

UCA and UCR

Maximum black
This indicates at which maximum intensity, the surface of black film is covered. The generation of the black is very important for a representation rich in contrast. In general, the maximum black should be roughly 95 %.

UCA (Under Color Addition or Addition of under-colors)
This term qualifies the addition of cyan, magenta and yellow in the pattern of neutral and dark sectors. Thus one can get black which is more saturated and richer in contrast.

UCR (Under Color Removal or Elimination of under-colors)
Most of the time the length of the black is calculated automatically by the software. When the cover of surface is regulated to minimum, the UCR does not replace the cyan, magenta, yellow in the neutral sectors by black. If the user sets up a UCR with a cover of surface more than 320%, the majority of the software automatically produce an addition of under-colors in the dark sectors.

UCR and GCR

GCR (Grey Component Replacement)
GCR, term also resulting from the traditional reproduction is, contrary to the UCR, a broad black which replaces parts of cyan, magenta and yellow with the colors saturated by the black. The majority of the programs of separation have a total adjustment for a strong or weak GCR.A strong GCR is a long and broad black. With a strong GCR and a weak cover of surface, one obtains the strongest possible reduction in quantity of colors for the impression. This combination is thus appreciated for non-art papers and in particular newsprints.A strong GCR can however also bring a transfer to the gray, when the printer puts more black than the program of separation expected.





Here is an UCR. The black starts only from 50 (1.) and goes up more and more until maximum 85 (2.). The rate of inking of the four colors together gives: Black: 85 Cyan: 79 Magenta: 70 Yellow: 70 = 304



Here is an UCR for newsprint. The black starts earlier to 30 (1.) and goes up to the maximum to 97 (2.).
The substitution of the black starts earlier and even more important is the dark tone. The goal is to have a low rate of fattening, since on newsprint one can print only with a maximum of 270 or even less.
The rate of inking of four colors together gives: Black: 97 Cyan: 64 Magenta: 51 Yellow: 52 = 264.




Here is an UCR with UCA. The black starts from 30 (1.) and goes up until maximum. 89 (2.).
Contrary to the pure UCR where three colors CMY remain on a certain level or even go down in the dark tone, the UCA still adjusts colors CMY in the dark tone. It results an image more contrasted in the dark tone. Used only on art papers, because the rate of inking is important.
The rate of inking of four colors together gives: Black: 89 Cyan: 94 Magenta: 82 Yellow: 81 = 346



Contrary to the UCR, the GCR substitutes colors CMY starting from the tone lights (1.) and throughout the coube of luminosity (2.). In the dark tone substitution becomes more important.
It results from it as favours an image with more neutral gray and a low rate of inking. Used for papers nonlying.
The rate of inking of four colors together gives: Black: 83 Cyan: 72 Magenta: 52 Yellow: 74 = 281



Here a GCR where the black begins (1. very early) and goes up to 83 (2.). Colors CMY are substituted in all the tone (long), but the rate of inking remains important (narrow).
advantage : Neutral gray. To use on art paper.
The rate of inking of four colors together gives: Black: 83 Cyan: 79 Magenta: 70 Yellow: 70 = 302

Points for the choice of the generation of the black
The following councils are approximate indices allowing to be good side. According to the software, pattern, printing works and paper etc...,rehandlings can prove to be judicious.

Choosing the cover of maximum surface for each category of paper:
for art papers: approximately 320 % - 360 %
for non-art papers: approximately 270 % - 300 %
for newsprints: approximately 220 % - 250 %

For non-art papers, and newsprint the black should be a little broader than for the art papers.
If your software does not allow these adjustments, the terms are partly different in each software. For each paper ,you can work with a maximum black of approximately 95 %

Choosing the adequate composition of black for each category of paper :
for art papers: a light GCR with addition of under-colors,namely a black skeleton
for non-art papers: an average GCR without addition of under-colors or UCR
for newsprints: an average GCR tests should be carried out before the GCR transfers the tone with the gray.

The Characterization

Before Characterise (creation of profile) your printer, it should be gauged.

Charts of impression in ICC profiles at the time of a proof impression

The charts determines the returned colors from the primary colours in the system of impression with an intensity of 0 to 100%. To determine these charts, one conducts a test which prints each primary color on paper with small steps between 0 and 100 % of the tone value. The chart now indicates the values in numerical way on the paper. Variations on these curves can bring the fluctuations on the balance of gray, for example in the case of thermal printers.

The printers proof works with different materials of impression brought an internal standard for each material of impression. With a measuring instrument, the curves of impression on the printer will be given for each material. If those diverge from the values given, one will calculate a curve of correction using a software of calibration thus bringing back the curves to the fixed standard.The curves can be recorded with the same measurement technique which is necessary for the determination of a profile (spectral photometer). But more specialized measuring instruments are better because they process much more quickly (densitometer) with these measurements. The special densitometers allow the withdrawal of complete bands of measurement. Unfortunately, few software exploit the combination of Rendering Intent and the curve of correction in order to create and manage ICC profiles. Certain RIPs are also intended for the correction of the curves.

          This stage of characterization is carried out via the impression of a charter IT8.7/3 (charter in the form of a numerical file). Measurements of proof are carried out using a spectrophotometer or a colorimetre and are compared with the numerical data of the original. The software then creates a printer profile being used as reference to the characterized peripheral. This characterization must be carried out rather regularly and on each different emulsion paper used in production, and with each change of ink.
An alternative can be used with this generic principle of characterization of printer. Qubyx proposes to use the scanner, whose calibration and characterization were already carried out, as a measuring apparatus. It is first of all necessary to be ensured to have a good scanner profile produced by KleoScanPro, and that it is stored in the folder Profils Colorsync. This function of characterization of printer is available with KleoPrint and KleoPrint Pro. Thus it is possible to create profiles of scanners and printers at the same time.

Current possibilities and materials

          In market, there are some tools which can be able to manage the color on the graphic chain. Materials of measurement such as the densitometers, colorimeters, spectrocolorimeters and spectrophotometers are manufactured by some companies (X-Rite, Minolta, Techkon, GretagMacBeth, Datacolor or Qubyx).
The software for creation of profiles for peripherals is more numerous and nowadays every one have a dedicated system to Color Management. The suppliers such as ColorBlind, ColorSavey, Color Solutions, Mona-coColor, Creoscitex, Heidelberger Druckmaschinen AG, Agfa, CandelaColor, Horses, Eastman Kodak, Barco, Aurelon, I-Proof etc, use their own personalized tools for the color management.

The Qubyx proposes a color management solution with the following products :

Qubyx Kleo, Kleo BASIC, colorimeters and software for the calibration and the characterization of the monitors
Qubyx KleoPro - Qubyx software for the calibration of the CRT and LCD Monitors and Spectrophotometre Gretagh-MacBeth Eye-One Monitor
Qubyx KleoPrint - software for the characterization of the scanner and the printer, usable without measuring apparatus (used for scanner when measurement of system)
Qubyx KleoPrintPro, software for the characterization of the scanner and the printer, with the choice of measuring apparatus. There are two types of spectrophotometers:

Qubyx Xenon - spectrophotometer having an interval of measurement equal to 5nm
Qubyx Spectro Counts - spectrophotometer XY for measurement of opaque and transparent charters, having an interval of measurement of 3 Nm.

Qubyx KleoKamera - software and sensor for the calibration of camera.
Qubyx KleoScan - software and sensor for the calibration of the film scanner.



The software Print Open™ from the company Heidelberger Druckmaschinen AG is very complete, and allows many possibilities of adjustment, especially for the creation of the black in profiles CMYK.

How to work with profiles?
working in CMYK, RGB or LAB?

work using Lab data

Advantages:
All the constituent parts of a document are treated in the color space Lab. After the completion of the document, the user converts it for media of edition of his choice by the means of an adequate profile of edition. Color Space Lab offers the greatest extent of colors. There is only small amount of loss, when numerical documents are converted in a color space with a restricted extent of colors. Contrary to the operating mode CMYK, the Lab data can be converted automatically on each standard of desired offset printing.

work using RGB data

This operating mode works in a uniform color space, instead of maintaining all the data directly in color space Lab. It is thus possible to exchange data RGB between various working stations, as long as all the working stations function with same color space RGB. In practice however, one can start working from different RGB standards. This is why it is important to agree before a project to work on common data RGB in a common color space RGB.
As many application programs could function with RGB data before the appearance of Color Managment, the exploitation of a color space RGB is developed much for the impression than the color space Lab. The standardization of the color space RGB and a numerical work in RGB made much more reliable, including the catalogues of nuanciers.

work using inserted profiles

The insertion of profiles in files allows the data exchange between the users who work with different manufacturing processes.The profile inserted in the file makes it possible to transform colors RGB or CMYK to the media of a file in color space Lab. Just like the Lab files, it is possible to transform RGB files or CMYK into the corresponding color space.
At the time of exporting of files, the profile of the workspace is usually inserted. Alternatively, the file can be also converted in the workspace of the following stage and the corresponding profile will be inserted. At the time of importing of a file, it is initially controlled. If this profile is identical to the workspace in progress, the file is directly taken. If the inserted profile and its workspace in progress are different, the data to be imported are modified in Lab by the inserted profile then transformed by the profile for the workspace in progress. At the moment when we print (Winter 2001), all the softwares do not function with the inserted profiles.
- PART II - CHAPTER I - The COLOR ON CHAINS GRAPHICS -
 
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