Control colour in pre press

This standard is about having control over the pre press workflow to ensure that colours are properly represented to the customer from the outset, and that the colours when printed are predictable and meet the customer's expectations and are within acceptable commercial parameters.

Workflows have developed to such an extent that it is essential that a Mac operator is competent in all aspects of correctly utilising the software. This includes understanding and correcting any errors or problems that are highlighted using the same or additional software. This is of particular importance as this is the hub for all pre press operations. Being competent and knowledgeable of the system and the workflow is imperative to make everyday operations easier and consistent. Workflows include software and workflow plug ins for adding the artwork to the system which facilitates further working of files, trapping, colour correction curves etc, and can be applied to suit individual presses or even substrates. This is also where a working knowledge of the relevant print and finishing processes is essential for the files to be imposed/stepped correctly for what is required.

A competent Mac operator should be able to understand and foresee issues with files from reading their setup. Examples are, applied filters, screen only fonts and images in the wrong colour profile. These should be recognised and corrected before an item can be passed and ready for press.

There is a difference in procedures between general print and print for packaging.

In general print, they tend to print more process colour work and proofs are 80% colour accurate. This is achieved by using calibrated devices at the proofing stage and working on files on calibrated equipment for colours. Most companies use CIP3 files and standard colour profiles like ISO standards. This can be linked to press technology where colour control strips are used and on press measuring can take place. 

In packaging, process colour work is used less so the starting point is previously agreed ink draw down samples which start life as a PMS reference and slowly evolve to form bespoke colours. These are generally passed on press at first print by the customer or a supplied "standard" is produced which is filed and used for each subsequent print run. For packaging, continuity is key and paper tone can also affect the outcome. Spectrophotometers are not normally used as they are ineffective if using a coloured or metallic paper for example.

It is common across both "industries" for compensation curves to be used. These are used to calibrate pre press equipment and are used to alter issues on press. Generally, these are set up to be alterations of -5%, -10%, +5% +3% for example, and can be used across a whole set of plates or for individual ones. They can be used to alter a specific area, but these are more bespoke and detailed. It is an important criteria that a Mac operator can do this. These are used in addition to dot compensation curves. A dot compensation curve is used to calibrate the CTP to allow the output of accurate plates. This is applied to every single plate that goes through the process and it is critical that the CTP is calibrated regularly to allow for this.

Problem solving is a required competence and being able to use the various software packages and the system/workflow is essential. Issues that occur while ripping will be highlighted within the system and you must be able to resolve these by altering the files. This can be due to internally placed artwork within your file, a print method or wrong settings.

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*          Calibrate and maintain pre press equipment*

1. calibrate display monitors in the workflow to produce accurate colour reproduction
2. calibrate all output devices to meet requirements, including image setter/CTP setter and proofer(s)
3. calibrate any scanners in the workflow to meet requirements
4. store any device profiles created during calibration of monitors, scanners and printers in the correct location in accordance with organisational requirements
5. check at regular intervals that all calibrated devices are still within calibration
6. adjust profiles or equipment parameters to bring devices back into calibration, allowing for various substrates
7. complete records of calibration checks in accordance with organisational requirements
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Utilise pre press software within the workflow

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8. assess the settings for each colour management feature in each software application against job requirements
9. check that any software colour management features that may alter the colour values are configured in accordance with organisational procedures
10. establish the linear curves and configure the application software or workflow to make allowance for this
11. establish the compensation curves and configure the application software or workflow to make allowance for this
12. save software settings once configuration is complete in accordance with organisational procedures
13. communicate with colleagues in accordance with organisational procedures
14. use appropriate reference material to check that hardware and software colour management configuration produces reliable colour reproduction on press and on 'high resolution' proofing device(s)

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Apply colour profiles/settings correctly

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15. select the correct destination profiles for outputting to specific devices
16. check that the correct source profiles are embedded in image files, assigning new profiles in accordance with organisational requirements
17. communicate the consequences when embedded source profiles are not correct or are missing in accordance with organisational procedures
18. assign profiles to files after conversion to new colour modes in accordance with organisational procedures
19. set all application software in the workflow to use source and destination profiles in accordance with organisational requirements

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1. the hazards and risks in your own job, their assessment and the action to take to deal with them
2. manufacturer's health and safety requirements relevant to your job
3. computer system security and virus protection
4. how to communicate with colleagues, customers and suppliers
5. workplace objectives, priorities, standards and procedures
6. the range of work carried out in the workplace
7. the set-up of digital imaging equipment and software
8. the operation of digital imaging equipment and software
9. colour theory and additive and subtractive systems such as RGB, CMYK colour gamuts
10. colour management and how to set up, maintain and use image profiles
11. how colour profiles, dot gain compensation or simulation, colour mode conversion or total ink content calculations can alter colour values in digital images
12. the principles of digital colour workflow, how it is configured and where colour mode changes and colour profiles are used
13. causes of colour shift and how to resolve them
14. the range of methods, equipment, material and software appropriate to the imaging requirements
15. the assembly and set-up of image editing and output systems
16. embedded information
17. file management procedures
18. file types and which files formats can carry embedded profiles
19. the nature and use of record-keeping systems
20. the main features of quality assurance and quality control systems
21. techniques for controlling quality, including inspection, testing, sampling, use of input and output controls
22. equipment for controlling quality in pre-press
23. techniques for solving complex problems
24. how cleaning, lubrication and maintenance can affect operation
25. the maintenance plans for machines which you operate
26. the principal types of proof and their role in the printing process
27. the operation of image editing and output systems