05 094 ImageControl EN RZ - Weeblymagnifisa.weebly.com/uploads/1/3/3/5/1335969/prinect.pdfPrinect...

Content

1 About these Guidelines 4

2 Fundamental rules and hints for proper

measurement 5

3 Features of Prinect Image Control 6

3.1 The key issues in brief 6

3.2 How Prinect Image Control works 7

4 Measurement principle 8

4.1 Color measurement 8

4.2 Color deviation ΔE 8

4.3 Density measurement 9

4.4 The benefits of spectral color measurement 9

4.5 Density and dot area measurement 10

5 Generating follow-up recommendations 11

5.1 Defining image areas as a reference 11

5.2 Storing color sets in the color archive 11

5.3 Ensuring of reference values 12

5.4 Generating follow-up recommendations 12

5.5 Changing reference values 13

5.6 Reasons for an incorrect deviation display 13

6 Control methods 14

6.1 Using control elements 14

6.1.1 Using color control strip 14

6.1.2 Using color control blocks 14

6.2 Measurement within the image 15

6.2.1 OK sheet 16

6.2.2 Use of copies 16

6.2.3 Multi-color image areas 17

6.3 Which control method to use & when? 18

6.4 From make-ready to production run 18

7 Data management with

Prinect Image Control 19

7.1 Data archives 19

7.2 Job protocol database 20

8 Prinect Image Control modules 21

8.1 Memory Plus – the “extended memory” 21

8.2 Color Interface – the way to the ICC profile 22

9 The limitations of Prinect Image Control 24

10 Sample jobs 25

10.1 CMYK job with text in special color 26

10.2 CMYK job with frame in special color 27

10.3 CMYK job with frame in two special colors 28

10.4 CMYK job with defined corporate color 29

10.5 CMYK job with high text component 30

10.6 Copy image area in CMYK with frame in CMYK 31

10.7 Copy image area in CMYK with frame in

special color 32

10.8 CMYK and special colors within the image 33

10.9 Job with special colors only,

using color control strip 34

10.10 RJob with special colors only,

using image control 35

10.11 CMYK job with different special color areas

in solid and screen 36

10.12 CMYK job based on a previous OK sheet

(partially or completely) 37

11 Glossary 38

Prinect Image Control About these Guidelines4

These guidelines provide background information designed to make it easier

to use Prinect® Image Control. They highlight individual functions and features

of Prinect Image Control and the applications for which these could be used.

The practical hints summarize important information. They have a grey

background.

The guidelines do not deal with the individual operating buttons of Prinect Image

Control in detail.

Information on individual operating steps can be accessed using the Help

function of Prinect Image Control or can be found in the operating instructions.

The Help function can be used by the operator when he is working on the unit.

The particular help is available based on the main menu which’s currently being

used. If you are currently located in the color archive, for example, you will be

able to access information to create a color set.

1 About these Guidelines

The Heidelberg logo button can beused to access the Help function.

Fundamental rules and hints for proper measurement Prinect Image Control 5

The following section sets out the key rules to ensure proper measurement

and color control.

Basic principles

• Prepare the press and Prinect Image Control (color archive, measuring

conditions and ensure valid calibration).

• Prepare a color set(s) based on standard material and standard inks

With every job

• Use presetting data from PPI/CPC31 or repeat job, if available.

• Use pre-inking 1 or 2.

• Do not pull the sheet to be measured too early as this can result inaccurate

follow-up recommendation. Take note of the “green light function” on the

Prinect® CP2000 Center®. Manual intervention should not be conducted

between two follow-ups.

• Since measurements are performed without polarization filter, the

printed sheet must be measured as soon as possible after sheet removal

to ensure a stable measurement and color control.

• It is generally a good idea to stop the press during the make-ready steps

rather than leaving it on idle speed. This retains the ink profiles in the

inking unit.

Goals

If preparations are performed properly, the measurement of the first sheet

pulled should show a color difference of ΔE < 8 (average value). With larger

color deviations, the characteristic curves “presetting” should be optimized.

If the presetting is OK, a color deviation of ΔE < 3 should be achieved within

two to three follow-up recommendations.

Correct measurement and control can only be assured if the inking/damp-

ening units rollers are set correctly and the dampening solution supply to

the plate is optimized.

2 Fundamental rules and hints for proper measurement

Prinect Image Control Features of Prinect Image Control6

3.1 The key issues in brief

Prinect Image Control is an external color measurement system to monitor

and control the printing quality. It is the only system worldwide which is capable

measuring the entire printed image spectrophotometrically.

Key features

• Up to four printing presses can be connected online to one Prinect Image

Control unit.

• Prinect Image Control can be integrated into the workflow using a network

link.

• Each measurement per side takes less than 30 seconds.

• A 70 × 100 cm print sheet can be measured in its entirety by breaking it down

into 160,000 measuring points. This enables the print quality to be assessed

over the entire print sheet.

• One measuring point is approx. 2.0 × 2.4 mm in size.

• For each ink zone, there are approx. 5,000 measuring points on a 70 × 100 cm

sheet. This means that the measurement is far more extensive than merely

viewing a color bar.

• The quality of the production run can be documented by printing out or

storing the relevant job protocols.

• Repeat jobs can be saved in the job database.

• The unit can be used to measure test forms, to export data to generate an

ICC profile and for process calibration.

• Through Remote Service, Heidelberg® branches can access the unit via a

modem connection if servicing is required.

3 Features of Prinect Image Control

Features of Prinect Image Control Prinect Image Control 7

3.2 How Prinect Image Control works

Brief description of a measurement:

1. The sheet is broken down into 520 columns and 310 rows during the

measurement process. All the cells (measuring points) are displayed in

order of measurement.

2. The light returned at the measuring points is passed into a spectropho-

tometer where it is broken down into its spectral colors.

3. The computer uses the spectrum of each measuring point to define the

Lab1 and unpolarized density values.

4. By comparing the colorimetric values which have been measured with

the reference values entered earlier, the necessary corrections (ΔF) can

be calculated and transferred by Prinect Image Control to the

Prinect CP2000 Center.

5. The Prinect CP2000 Center passes the follow-up recommendations to the

ink fountains of the individual printing units where they are immediately

implemented.

The “Illuminant” and “Standard observer” parameters should be preset to

D50 and 2° in accordance with DIN ISO 13655.

Printed sheets

Lightsource

Spectrometer

Spectrum

380 nm 720 nm

Computer/PC

Printing press

Prinect CP2000 Center

1 The correct notation is L*a*b*. Lab will be used throughout this text by wayof simplification.

Prinect Image Control Measurement principle8

This section deals with the principles for measuring with Prinect Image

Control. It only touches briefly on the basics of colorimetry. More infor-

mations in our brochure "User Guide: Introduction into Colorimetry and

Spectrophotometry" (www.heidelberg.com).

4.1 Color measurement

A Lab value can be calculated from every color spectrum. This Lab value

represents an unique color impression.

The following example shows how a color is assigned to its spectrum

and the Lab values calculated from it.

4.2 Color deviation ΔE

The Lab color space is matched to the perception of the human eye. Color

deviation which is perceived as being of the same intensity has the same

distances in all color tones. This color deviation is known as ΔE (Δ = “delta”).

The L value describes the lightness; a and b represent position on the

RED-GREEN axis and YELLOW-BLUE axis respectively.

4 Measurement principle

L =

a = –

b =

59.4

56.7

49.3

400 500 600 700 nm

Actual

Reference

WhiteΔE < 0.2 not visible deviation

0.2 – 0.5 very small deviation

0.5 – 1.5 small deviation

1.5 – 3.0 fair deviation

3.0 – 6.0 clear deviation

6.0 – 12.0 large deviation

> 12.0 very large deviation

S (λ)The conversion was defined by the CIEcommission. CIE stands for CommissionInternational de l’Eclairage. In English:International Commission on Illumination.

Measurement principle Prinect Image Control 9

4.3 Density measurement

Color density measurement primarily involves measuring the intensity of a

printed color.

The density value depends on the thickness of the ink film printed, the color

filters used (red-green-blue filter) and the use of polarization filter.

It is also possible to measure the density of special colors, although this is

not sufficiently reliable.

An unpolarized density value (in accordance with DIN 5033) is ensured by

Prinect Image Control based on the spectral measured values. The polarized

density display is calculated as a theoretical value.

Range of

density measure-ment with

magenta filter

400 500 600 700 nm

Range of

density measure-ment with cyan

filter

400 500 600 700 nm

400 500 600 700 nm

Range of


yellow filter

4.4 The benefits of spectral color measurement

The following example shows two entirely different colors. They can be

differentiated using spectral color measurement, while the density measure-

ment is unable to detect any deviation in color as using and displaying the

highest density reading only.

The same filter color (yellow complementary filter) is used for measuring

the density of both colors.

Prinect Image Control Measurement principle10

Densitometric measurements are “color blind”. This means that a specific hue

can only be measured using spectral color measurement.

4.5 Density and dot area measurement

In essence, ink film thickness (color density) and dot gain define the color

impression.

In the color control process, the only target parameter varied and/or con-

trolled is the ink film thickness. The dot gain is also influenced by this process.

The dot gain is calculated using the Murray-Davis equation (from density

values).

In each case, spectral color measurement examines the entire spectrum of

the colors. The Lab values that are calculated are used to determine the color

deviation of ΔE = 114.4 between the two colors.

Color sample HKS 8 Density and Lab values

Density and Lab values

Spectrum of HKS 8

Color sample HKS 65

400 500 600 700 nm

Spectrum of HKS 65

D =

L = a = -b =

1.60

59.456.749.3

D =

L = a = b =

1.60

60.256.862.9

Range of


yellow filter

Range of


yellow filter

400 500 600 700 nm

Col

or d

ensi

ty in

full-

tone

DV

2.52.0

1.71.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0% 0

0,1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.91.0

1.5

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

FOGRA

Dot

are

a A

Col

or d

ensi

ty in

scr

een

DR

Generating follow-up recommendations Prinect Image Control 11

5.1 Defining image areas as a reference

A measuring run basically involves capturing all image areas of a sheet, even

if only individual areas will be used as references later on throughout the

production run.

Follow-up recommendations are determined as soon as measured values and

reference values for a sheet are available for comparison.

Since inking can only ever be set on a zonal basis, follow-up recommendations

only ever apply to one particular ink zone. This means that diverse areas can serve

as a reference for calculating the follow-up recommendations:

a) All image areas on the printed sheet (e.g. from the OK sheet)

b) Partial areas of a sheet (e.g. repeats, frames, etc.)

c) Color control strips

d) Combination of a–c

5.2 Storing color sets in the color archive

In principle, a color set comprising B/C/M/Y can also contain any number of

special colors.

Three types of paper (glossy, matt, uncoated) are stored for every color set.

The paper white that is used is saved in each color set. When creating a color

set, the paper white must always be measured first. The color values are then

loaded next. After ascertaining the target values of the scale, the Lab value of

the Heidelberg gray patch (C70%/M60%/Y60%) can be optionally stored; this

then serves as a reference for the gray patch measurement (CMY).

Only color values from natural samples can be loaded into the database.

5 Generating follow-up recommendations

Ink

fadi

ng

Indi

vidu

al in

k zo

ne

Prinect Image Control Generating follow-up recommendations12

5.3 Ensuring of reference values

The term color sets refers to colorimetric default values of primary, (process)

and special colors.

As different types of ink have different printing and colorimetric characteristics,

these have to be stored separately in the Prinect Image Control color archives.

This means that a test print with the particular ink/paper combination has to

be evaluated.

The Lab values from the “process standard for offset printing” (or DIN ISO

12647-2) can also be used as the basis for this evaluation (see table below).

Furthermore, lab proof strips or existing color samples can be loaded.

Gray patch measurement: If the values for the color set are defined according

to the procedure above, the values for the gray patch should also be loaded.

Values for black substratePaper type 1 + 2 4

glossy and matt coated white offset uncoated

L* a* b* L* a* b*

Black 16 0 0 31 1 1

Cyan 54 –36 –49 58 –25 –43

Magenta 46 72 –5 54 58 –2

Yellow 88 –6 90 86 –4 75

Red (M+Y) 47 66 50 52 55 30

Green (C+Y) 49 –66 33 52 –46 16

Blue (C+M) 20 25 –48 36 12 –32

Measurement in accordance with DIN ISO 13655, D50 illuminant, 2° observer, 0/45 or 45/0 geometry.

5.4 Generating follow-up recommendations

If the reference values have been selected from the color archive, the first

production run measurement can begin.

• The measurement system first of all performs a position measuring run which

records the sheet size and sheet position (drive side/operator side).

• Then the image areas to be used for the color control process (reference/actual

comparison) have to be defined. During the image measurement process, it is

possible to scan in e.g. samples (size 1:1) through the submenu “Image Area

from Sample”.

A follow-up recommendation per ink zone is calculated immediately after the

measuring operation.

Generating follow-up recommendations Prinect Image Control 13

5.5 Changing reference values

If modifications for the target reference values are required during the color

matching process, these can be done by changing the percentage. The unit

automatically calculates the corresponding Lab value and displays the color

distance ΔE. Zonal OK areas, for example, can be adopted and/or others adjusted

during color matching.

5.6 Reasons for an incorrect deviation display

In a few rare cases, Prinect Image Control will output high color deviations

(see image) even though the print looks to be fine.

This can be due to a number of causes:

• Wrong color set and/or wrong paper white has been selected

• Printing ink deviates from the color set displayed by a high ΔE0.

• Different print conditions

• Wrong measuring conditions selected.

If the measuring conditions and color set are set correctly and there are still

large deviations, the reference values should be checked.

All possible steps for reference value correction should only be performed in

stages and in a well-directed manner. Changes in the reference value during

the production run can lead to color fluctuation.

Prinect Image Control Control methods14

6.1 Using control elements

Using control elements can be subdivided into control using color control

strips and, for example, color control blocks distributed as required.

6.1.1 Using color control strips

Using color strips is easy. It is very well suited for the make-ready of a job if

no OK sheet is available.

By measuring and controlling solid patches, a color set is required that

contains the L*a*b* values for all printing inks and the paper white.

With gray-patch control (gray balance patch C 70%, M 60%, Y 60%), the

operator must ensure that the value corresponds to the appropriate color set. If

problems are encountered with the gray-patch measurement, it should be en-

sured that the values of the dot areas are reproduced on the plate correctly.

Control using color control strips also supplies values for process monitor-

ing. These can include: Dot gain, slur/doubling, ink trapping. The illustration

shows a section of a color control strip. We can see the solid patches for cyan,

magenta, yellow and black and the gray patch (CMY). A line screen is also dis-

played to determine slur and doubling errors. The individual period repeats

over all the zones of the print sheet.

6.1.2 Using color control blocks

Color control using color control blocks is very similar to control using color

control control strips. In both cases, particularly developed control elements are

used for the color control. The difference between the two procedures lies in how

these control elements and their patches are arranged.

The color control strip is positioned horizontally and repeats periodically

over the entire sheet.

Color control blocks can be positioned either horizontally or vertically.

They do not repeat cyclically and can be applied to any point on the sheet.

However, color control cannot take place in an area where no color control

blocks are located. Thanks to their structure, color control blocks are par-

ticularly well-suited for print checks in packaging printing, for example, since

they can be applied extremely well to the trim between the individual repeats.

The predefined color control blocks can be used to check the various important

printing parameters. The following blocks show different control patches.

6 Control methods

7 8

Prinect 4GS Dipco 2.0 Format 52 © 2003 Heidelberger Druckmaschinen AG

Control methods Prinect Image Control 15

6.2 Using image measurement

Control using image measurement has the following benefits over control

using color control strips and/or color contol blocks:

• Far more measured values are obtained per zone (approx. 5,000 per zone

on a 70 × 100 cm sheet) as when using control elements.

• Since the measured values are averaged over the circumferential direction,

they are more informative than measured values obtained at just the start

of printing or just the end of printing.

• All tonal values of the print image are captured in the measurement and

taken into account in the control procedure.

• Control is performed primarily on the basis of the print image, i.e. the

object that will be sold and not the marginal areas.

• In principle, image control without color control strip is possible. Although

this means that paper can be saved, it is then no longer possible to monitor

the process parameters.

Compared to control using color control strip and/or color control blocks,

image control can sometimes appear less stable. The reason for this is

not to be found in the quality of the control process, but rather the fact that

process-related fluctuations are more recognizable.

The following processes are supported for image control:

• OK sheet

• Image areas

• Multicolor (homogeneous) image areas

The following pages look at these procedures in detail.

color contol block for checkingsolid patches.

Color contol block for checking the solid, 70% dot gain and slur/doubling errors.

Color contol block for checking the solid and 25%, 50% and 75% dot gains.

Color contol block for checking the solid and 40% and 80% dot gains.

1

2

3

4

Color contol blocks 2 to 4 are available for all colors of control block 1.


6.2.1 OK sheet

There are two options to make-ready a repeat job:

a) Load the job from the job archive. This procedure reduces the make-ready

time, the amount of waste and ensures the use of the same measurement

conditions.

b) Scan in the values of an approved OK sheet.

There are three options for adopting the OK sheet:

a) Entire sheet

b) Color control strip

c) Partial OK areas of the sheet

During image control, only the measuring points that satisfy the following

requirements are included in the control process:

• The measuring points are located in image portions that are at least

6 × 6 mm.

• The color component in the image area to be controlled has to display

sufficient ink coverage for each of the individual colors.

• The areas to be controlled consist either of process colors or a maximum

of two special colors in a composite print.

The example opposite shows a classic jobfor control using the OK sheet. The exampleshows screen tones constructed fromprocess colors, and a full-tone frame in thespecial color blue.

6.2.2 Use of copies

Color control using the function “Copy Image Area” is always employed when

there are multiple copies of the same type on the sheet.

The illustration shows a printed sheet that is ideal for control using copies.

With this type of control, the color of a copy is defined as the colorimetric

reference. A Lab reference value is generated for each measuring point on this

copy. These reference values are transferred to the remaining copies. When

measuring the next sheet, the follow-up recommendations are generated from

the deviation between the reference values and the actual values, meaning

that the best possible color match could be achieved for all selected copies.

Control methods Prinect Image Control 17

Mixed forms (several different copies one after another) can be applied as

a reference value.

When using this method, the image area must satisfy the following requirements:

• There are several identical copies on the print sheet. These can be rotated

either by 90º, 180° or 270°.




6 × 6 mm.



6.2.3 Multicolor image areas

Control using multicolor image areas (hues from process colors or a maxi-

mum of two special colors) can always be used if there are homogenous

screened or solid areas on a sheet.

The graphic shows a printed sheet which is suitable for control using

homogenous image areas.

The gray area is made up of process color separations. A Lab value is

defined for this image area and used for control.

When using homogenous image areas, the image must satisfy the following

requirements:


6 × 6 mm.





Homogenous image area


6.3 Which control method to use & when?

• Control using color control strips is ideal for getting to know Prinect

Image Control. This method is very well suited for setting up jobs. Color

control strips are perfect for low area coverages on a sheet and for text as

well.

• Control using color control blocks is always ideally suited if blank areas

are not located along the margins of the sheet, but rather at various

locations on the sheet. A color contol block can be easily positioned in the

blank areas. This situation frequently occurs in packaging printing.

• Color control using OK sheets is a standard control method for achieving

stable results over long production runs.

• Color control using the function copy image area is limited to multiple-up

sheets. This type of control is ideal for compensating and preventing color

fluctuations across the printed sheet. Image areas can be saved in the

database “Image Area”.

• Color control using multicolor (homogenous) Image areas is suitable if

specific homogenous image areas need to be kept as constant as possible,

e.g. when printing color swatches or corporate colors.

All control methods can be combined as desired.

6.4 From make-ready to production run

The process of printing a job is outlined below by way of example:

1.) Set up job.

2.) Check measuring conditions.

3.) Select color set and type of paper. These must agree with the material

currently being used!

4.) Perform first measurement.

5.) Position color control strip.

6.) Adjust until the required tolerance is achieved. Perform any fine correc-

tions that are needed.

7.) Define OK sheet.

8.) Cyclical measurement and release the follow-up recommendation. Ensure

the press run is stable between measurements. Avoid pulling and measur-

ing the sheet too early (➔ green light!).

This procedure can change depending on the modules used and the type of job.

Make-ready using color control strip and production run printing using

the “OK sheet function” is only to be understood as illustrative in nature.

In addition to make-ready using color control strip, make-ready can also

be performed using color control blocks, repeat jobs (control using OK sheet).

In addition to the OK sheet, color control methods in the production run

can be performed using color control strips, color control blocks, image areas

or homogenous multicolor image areas.

All color control methods can also be combined with each other.

Data management with Prinect Image Control Prinect Image Control 19

7 Data management with Prinect Image Control

7.1 Data archives

Prinect Image Control has various data archives. The individual archives are

accessed during order processing on Prinect Image Control. The job and color

archives can therefore be accessed when setting up a job. When defining a

color control strip access is made to the color control strip archive.

Changes to the archive in question are made via the Prinect Image Control

Service menu. This menu can be used to select the relevant archive. The indi-

vidual archives are presented in brief below.

Job

The job is saved under the job name and date. When loading a job, the precise

measurement and control conditions under which the job was processed are

restored. In this way, for example, the reference values of an OK sheet can be

reactivated. It is only advised to save a job if a repeat job is anticipated since

the archive has only limited capacity.

Color

This archive is used to save color sets.

The saved Lab values for a color set are stored with the corresponding paper

white each. If a color set is used on a different paper, Prinect Image Control

indicates reference values other than those in the color archive. This is not

a fault in the unit. Instead, the unit is attempting to create the same colors

as on the original, taking into account the change of paper white. The first

measurement matches the reference values to the newly calculated paper

white.

Press

The press archive contains the most important data for all interfaced presses.

This archive only has to be accessed when the machine fleet is changed or

extended.

Color control strip

This archive stores color control strips and color control blocks. For greater

transparency, it is possible to differentiate between color control strips and

color control blocks that are used and those that are hidden or unused. This

makes it easier to locate control elements when processing jobs since, when

positioning the control elements, only the color control strip and/or color

control blocks that are actually used are made available for selection. Color

control strips and color control blocks can be loaded by disk or CD-ROM.

Tolerances

The Tolerances archive is used to save tolerance values in ΔE for the process

colors, special colors and the complete image.

Tolerance values are defined in percentages for the 70% screen patches,

the slur and doubling elements and the density values.

If the tolerance values are exceeded, this is highlighted in color. Tolerance

values have no influence on determining the recommended color corrections

Prinect Image Control Data management with Prinect Image Control20

and follow-up recommendations, only on the deviation display. The tolerance

classes “narrow”, “average” and “wide” are already predefined. These tolerance

values can be changed as required and additional tolerances could be input as

well.

Database backup

This function can be used to copy the entire database (at cyclical intervals if

set appropriately), thereby preventing the possible loss of important data.

If a connection exists to a network, a copy can be saved at any location in the

network.

7.2 Job protocol database

The Prinect Image Control Overview menu can be used to create five different

job protocols. All job data are saved in an Access database. The protocols are

created from this database.

A trend protocol can be output in graphical or numerical form for a pro-

duction run. It is also possible to output a production run overview. The zonal

color for an individual sheet can also be viewed in graphical or numerical form.

The trend protocol shows the average ΔE deviation of a sheet from the

relevant reference value – and can do so for each color.

The production run overview protocol relates to saved tolerance limits

and shows the percentage of measured sheets that are inside/outside these

tolerance limits.

The zonal color protocol lists the measuring results of the individual

colors for the sheet last measured and does so for the relevant ink zones. It

contains different measured values depending on the control type selected.

When using color control strips or color control blocks, the measuring results

for the relevant control patches are output. When using image as reference

only ΔE deviation is displayed.

Protocols can be saved locally or in the network. When saving them in the

network in conjunction with the “Proto Viewer” add-on software, records can

be accessed at any workstation of your choice. Each user can also develop his

own evaluations using the Access data format.

In addition to individual sample sheets, these protocols provide valuable

documentation for convincing customers of consistently high quality in the

production run.

Prinect Image Control modules Prinect Image Control 21

8 Prinect Image Control modules

Modules refer to software add-ons to Prinect Image Control which can be used

to optimize the workflow in the printshop. Different modules can be used

depending on the printshop’s size and structure.

8.1 Memory Plus – the “extended memory”

When repeat jobs are received, the operator can access the original job saved

in the database. This database has storage capacity for around 250 jobs.

The Memory Plus module can be used to save and manage several thou-

sand jobs together with all important machine settings such as the job

number, job name, paper format, production run and ink zone setting.

The data volume for a job depends on the control type. For example, image

control involves saving far more data than control via color control strips.

The “Data management with Prinect Image Control” section provides

further information on the “Job” archive.

Prinect Image Control Prinect Image Control modules22

8.2 Color Interface – the way to the ICC profile2

All the devices involved in the production process (such as screen, printer or

proofer) simulate the end product, the printed sheet. It is therefore useful to

have a separate profile for each device which describes their gamut. Color

Interface supports this profile generating process by generating color measure-

ment values (L*a*b*) reliably and quickly. The Color Calibration test form has

been particularly developed for generating and compensating those profiles.

The illustration below shows the entire test form with all required measur-

ing patches (in accordance with ICC guidelines). The relevant measuring areas

are marked in red. The text shows the information supplied by the individual

areas. The ink fading, color chart and dot gain areas are available in duplicate.

Only one of the two areas is labeled in each case. Different images are provi-

ded for visual assessment purposes.

The color charts supply the color measurement values for generating the

profile. All measurement data is exported to the software specifically used for

profile generation.

The other parameter fields show the process parameters of the printing

press. Color Interface generates an appropriate protocol for all process para-

meters. Prinect Image Control enables the user to create profiles and monitor

production on a single unit.

Prinect Image Control is ideally suited to analyzing test charts (IT8, ECI, etc.)

as part of the color management process. The measurement operation lasts

only 30 seconds and is therefore far superior to other measuring systems.

2 The idea of the ICC profile was developed bythe International Color Consortium.

Prinect Image Control modules Prinect Image Control 23

Each output unit has its own gamut. The illustration shows the gamut for:

a) Color photography

b) High-quality offset printing

c) Newspaper printing

The aim of each profile generation process is to adapt a limited gamut

(e.g. offset printing) to fit a larger one (e.g. monitor).

Use of a profile and monitoring of the necessary parameters combine to

ensure true-color results in print.

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.00.10.0 0.2 0.3 0.4 0.5 0.6 0.7

a b

c

Prinect Image Control The limitations of Prinect Image Control24

9 The limitations of Prinect Image Control

Prinect Image Control has been designed for a wide range of applications in

offset printing.

The following applications involve some limitations:

• Measurement and control of metallic inks

• Metallized printing substrates

• Transparent printing stocks

• Opaque, non-transparent printing inks

Control with low area coverages

• The measuring points are located in image areas that are at least 6 × 6 mm.

• Text and lines as shown by the illustration should be controlled via color

control strip. The measuring equipment cannot capture such small struc-

tures precisely enough.

Comparison of measuring results

If you wish to compare measuring results from Prinect Image Control with

those from other measuring devices, it is important that the measuring con-

ditions are identical in both cases. As of parameters such as density filter

standard, polarization filter, standard illuminant and standard observer, the

external measuring conditions such as the time elapsed between printing

and measurement and measurement in wet and dry conditions must agree.

Since Prinect Image Control does not have a physical polarization filter,

measuring wet sheets with polarization filters may result in deviations between

measuring results obtained using Prinect Image Control and those obtained

from other devices. These deviations can occur as Prinect Image Control calcu-

lates polarized density values from the unpolarized measurement.

Differences can also result from the calibration status of the particular

measuring device. The Service menu of Prinect Image Control contains a

function for monitoring the unit’s calibration cycles. Prinect Image Control

indicates every 3 months that it needs to be recalibrated.

Sample jobs Prinect Image Control 25

10 Sample jobs

The following pages describe the procedure for setting up typical jobs using

Prinect Image Control. There are many possible alternatives to the individual

operations described. Consequently, the descriptions given can only hope to

serve as a starting point for creating your own jobs and are not intended as an

comprehensive description of the unit’s capability.

The headings of the individual sample jobs provide information on the

structure of the images. This is further explained using an illustration. The

process of setting up the job is then described step by step.

As a general rule:

• If the adjacent areas of a color are smaller than 6 × 6 mm, control must

be performed using color control strip or color control blocks.

• If the color areas are 6 × 6 mm or greater, it is possible to choose freely

between all control types.

• Perform cyclical measurement and follow-up when carrying out control

measurements. Ensure the press run is stable between measurements. Do

not pull the sheet too early (➔ green light function).

10.1 CMYK job with text in special color

Control: CMYK and special color controlled via color control strip.

Setup procedure:

1. Set up job and select color set for the process colors.

2. Perform first measurement.

3. In the “Printing unit basic setup” menu, activate the “Select color from

sheet” function.

4. Show the solid area of the special color, transfer the value to the printing

unit and exit the menu.

5. Select the required color control strip from the list in the “Color control

strip Menu” and position it as appropriate. Exit the menu.

6. The follow-up recommendations are displayed in the “Overview” menu.

Note:

The special color must be present on the sheet in the required hue for the

“Select color from sheet” function. Otherwise it is possible to import “Select

color from sample” or “Select color from data base”. It is also possible to input

a Lab value for the special color using the “Enter value” function.

Prinect Image Control Sample jobs26

Color control strip for CMYK and special colors (e.g. Prinect 6S)

Text in special color gray

Image area in CMYK


10.2 CMYK job with frame in special color

Control: CMYK controlled via color control strip, special color controlled in

image.

Setup procedure:




sheet” function.

4. Show the solid area of the special color and transfer the value to the

printing unit.

5. Select the “Special color solid areas” button. (Solid areas in the hue of the

special color flash.)

6. Adopt the value and exit the menu.

7. Select the required color bar from the list in the “Color bar” dialog box and

position it as appropriate. Exit the menu.


Note:

The special color must be present on the sheet in the required hue for the

“Select color from sheet” function. Otherwise it is possible to import “Select

color from sample”or “Select color from database”. It is also possible to input

a Lab value for the special color using the “Enter value” function.

Color control strip for CMYK (e.g. Prinect 4GS)

Border in special color blue

Image in CMYK


10.3 CMYK job with frame in two special colors

Control: CMYK controlled via color control strip, special color controlled in

the image.

Setup procedure:




database” function.

4. Select the individual special color from the database, assign it to the

printing unit and confirm the special color by clicking “Enter”.

5. Once every printing unit has been assigned the reference value of the

printed special color, exit the menu.

6. In the “Edit reference values” menu, select the “Multicolor image areas”

button.

7. Select the “Color from sheet”button.

8. Show the composite print area of the special colors and confirm the hue

with “Enter”.

9. Select the “Special color layout” button.

10. Select printing units whose colors are used to construct the hue, confirm

with “Enter” and exit the menu.


strip” menu and position it as appropriate. Exit the menu.


Note:

Areas with more than two special colors in the sujet cannot be controlled in

the image.


Image in process colors

Border out of two special colors printed as homogenous solids or screen solids.


10.4 CMYK job with defined corporate color

Control: CMYK controlled via color control strip and image.

Setup procedure:





4. In the “Edit reference values” menu, select the “Multicolor image areas”

button.

5. Select the “Color from sheet” button.

6. Show corporate color with reference coloring and confirm with “Enter”.

7. Select the “CMYK color layout” button, confirm with “Enter” and exit the

menu.


Note:

The corporate color must be present on the sheet in the required shades for

the “Color from sheet” function. Otherwise it is possible to import “Color

from samples” or “Color from database”. It is also possible to input a Lab

value for the corporate color using the “Enter value” function.


Background in corporate gray, image in CMYK

Image in CMYK


10.5 CMYK job with high text component

Control: CMYK controlled via color control strip.

Setup procedure:





4. The control recommendations are displayed in the “Overview” menu.

Note:

Because of the low area coverage values for the images, the control recom-

mendations for image control can be less reliable. For this reason, it is re-

commended for jobs with a high text component to use color control strip

or color control blocks.

Color strip (e.g. Prinect 4GS)

Print sheet with high text component and little image information


10.6 Copy image area in CMYK with frame in CMYK

Control: CMYK controlled via OK areas in the image.

Setup procedure:



3. In the “Edit reference values” menu, select the “Copy image areas”

function.

4. Leave the default function “Image area from sheet” activated.

5. Show the image area with the required coloring level.

6. Select the “Search areas” function. (All repeats that are found will flash.)

7. Using the “Transfer OK-image area” function the reference values will be

transferred to all identically image areas. Then exit the menu.


Note:

Image areas must be present on the sheet in the required coloring level for

the “Image area from sheet” function. Otherwise it is possible to import the

coloring level for an image area using the “Image area from sample”, “Image

area from other side” or “Image area from CPC proof” functions.

Border in CMYK

Image in CMYK


10.7 Copy image area in CMYK with frame in special color

Control: CMYK and special color, controlled in separate areas in the image.

Setup procedure:




sheet” function.

4. Show the solid area of the special color with reference coloring on the

print sheet and transfer the value to the printing unit.

5. Select the “Special color solid areas” button. (Solid areas in the shade of the

special color will start flashing.)

6. Adopt the value and exit the menu.

7. In the “Edit reference values” menu, select the “Copy image area”

function.

8. Leave the default function “Image area from sheet” activated. Show image

area with the required coloring level.

9. Select the “Search areas” function.

10. Once all image areas have been located, transfer the color values for the

target repeat to the located repeats using the “Transfer OK-image area”

function and exit the menu.

11. The control recommendations are displayed in the “Overview” menu.

Note:

Areas with special colors and process colors must be defined separately from

each other.

Border in special color

Image in CMYK


10.8 CMYK and special colors within the image

Control: CMYK and special color controlled via color control strip.

Setup procedure:

1. Set up job and select color set for the process inks.



sheet” function.

4. Show the solid area of the special color with reference coloring on the

print sheet, transfer the value to the printing unit and exit the menu.




Note:

In the example, the process and special colors are overprinted in the same

image areas. The image control can therefore not differentiate between areas

with special colors and areas with process colors plus special colors on top.

This means that adjustment recommendations for in-house control tend to be

unreliable. For this reason, it is recommended for this type of job to use color

control strips or color control blocks as control method.

Background in the special color, screen built

Color control strip for CMYK and special color (e.g. Prinect 6GS)

CMYK image and special color, screen builtand mixed with process colors.


10.9 Job with special colors only, using color control strip

Control: Special colors controlled via color control strip.

Setup procedure:

1. Set up job, deactivating the “CMYK colors” button.



sheet” function.

4. For each special color, show a solid area with reference color on the print

sheet (e.g. in the solid patch of the color control strip), transfer the value

to the printing unit and exit the menu.




Color control strip (e.g. Prinect 6GS)

Image in special colors printed next to each other.


10.10 Job with special colors only, using image control

Control: Special colors controlled in image.

Setup procedure:

1. Set up job, deactivating the “CMYK colors” button.


3. In the “Edit printing units” menu, activate the “Select color from sheet”

function.

4. For each special color, show the solid area with reference color on the


5. Select the “Special color solid” button. (Solid areas in the hue of the special

color flash.) Adopt the value for each printing unit.


Image in special colors (solid) printed next toeach other.


10.11 CMYK job with different special color areas in solid and screen

Control: CMYK controlled via color control strip, special color controlled

image.

Setup procedure:




sheet” function.

4. For each special color, show the solid area with reference color on the


5. Select the “Special color solid areas” button. (Solid areas in the shade of the

special color will start flashing). Adopt the value for each printing unit

with special color.

6. Select the “Special color screen areas” button and the relevant printing

unit. (Screen areas in the hue of the special color will start flashing)

7. Adopt the area for each printing unit.




Note:

The “Special color screen areas” function enables Prinect Image Control to

differentiate between screen areas in CMYK and screen areas in special colors.

The function does not allocate a target value to the screen area in special

colors. When an OK sheet is generated, reference values are also assigned to

the screen areas in special colors.


Image in process colors (solid and screen)printed next to each other and/or overprinted.

Background in special colors (solid and screen).


New printed sheet

10.12 CMYK job based on previous OK sheet (entirely or partially)

Control: CMYK controlled image.

Setup procedure:



3. In the “Edit reference values” menu, activate the “Copy image areas”

function.

4. Select the “Image area from sample” function.

5. Place the old OK sheet on the measuring table and perform a measure-

ment run.

6. Show the required image areas.

7. Select the “Search areas” function. (All image areas that are found on the

new print sheet will start flashing).

8. Once all image areas have been found, transfer the reference values to the

found image areas using the “Transfer OK-image area” function and exit

the menu.

9. The follow-up recommendations are displayed in the “Overview” dialog box.

Note:

The complete OK sheet can be regarded as a copy if the old OK sheet and new

print sheet are identical. An old, non-yellowed label/sample can also be used

as an OK sheet.

Old OK sheet

Only parts of the oldOK sheet are identi-cal to the new job.

Prinect Image Control Glossary38

11 Glossary

Color management

Method/system for coordinating the individual units and presses involved in the

workflow from color image processing to finished print result. Color manage-

ment is used to guarantee correct color reproduction from input to output, e.g.

on printing presses.

Densitometer

A density measurement device. Reflective densitometers are used for the

printing process. To determine the density, the result of a white measurement

is set in relation to the measurement of the required color area. Density

Density

The degree to which an ink layer is impermeable to light. On a theoretical

level, this is the relationship between a measurement on unprinted paper and

a measurement on printed paper.

Printing profile

The graphical representation of the relationship between the dot areas of the

prepress products, generally screen data and the associated dot areas (screen

percentages) on the printed sheet. Dot gain

Ink fading

Term for the decline in the thickness of the ink layer in circumferential

direction in offset printing.

Color distance ΔE

ΔE describes the difference between two colors and can be calculated as the

distance of the Lab values between two colors.

Ink film thickness/ink level

The physical thickness of the applied ink. The ink film thickness essentially

determines the density value of a color.

Ink coverage

The ratio of the area covered (with image elements) to the total area (full solid).

The ink coverage is generally specified as a percentage. A distinction is made

in print between the effective ink coverage calculated from optical measure-

ments and the geometric ink coverage calculated from area measurements.

Actual value

The value actually measured for a sample. Reference value

Glossary Prinect Image Control 39

Metameric colors

Colors with different spectra that have the same Lab values under a given

illuminant and different Lab values under different illuminants. This is also

known as metamerism.

Nanometer (nm)

Unit of length, 1 nm = 0.000001 mm. For example, a fine hair has a diameter

of 0.020 mm, one thousandth of this would be 0.000020 mm, i.e. 20 nm.

Standard observer

2º or 10º

A test series is used to determine how the color perception of the average stand-

ard observer is linked to a specific color area. The 2° test setup reflects a typical

situation for reading books and magazines. The 10° test setup simulates

viewing of a billboard.

Polarization filter

The polarization filter can be connected upstream of the density measure-

ment. Polarization filters filter out the glare components of the light. This

makes the measurement virtually independent of the sample’s drying status.

One disadvantage, however, is that the density of the sample changes when

the polarization filter is used.

Reference value

Target value for a measuring sample. The aim of every control operation is to

ensure the smallest possible deviation between the reference value and the

actual value. Actual value

Dot gain

The difference between the dot area of the printed sheet and the dot area of

the printing plate.

Wavelength

The physical length of a wave period.

1 m

2° or 10°

Wavelength

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