An Introduction to Calibration and Device Profiling
Paul Lindström discusses the benefits of ICC technology and the ability to preview colours in your artwork as they will appear in the final print, which will help avoid colour errors, reduce waste, save time, money and stress.
It’s now 25 years since the International Color Consortium (ICC) was formed and the ICC colour management technology introduced. The ICC started as a joint effort between Adobe, Agfa, Apple, Kodak and Microsoft. Their idea was that colour management should be done starting at the computer operating system level, and that all applications should do it in the same way. This would add both consistency and ease of use.
The ICC invented a standard file format for colour conversions: profiles. The ICC’s colour scientists also decided that colours should be defined neither in CMYK (Cyan, Magenta, Yellow and black, called K because it’s the Key colour) nor RGB (Red, Green, Blue) colour spaces, because doing so limits what can be done with the colour data. Instead the ICC technology is based on the CIE Lab and CIE XYZ colour spaces which are much larger. These colour spaces are collections of mathematical definitions of all the colours humans can perceive, which is way more than either CMYK or RGB can represent.
Why a device independent colour space?
The ICC’s approach defines colours within a much larger colour space than the CMYK or RGB colour spaces, so that how they look is not influenced by the peculiarities of a particular imaging device. Inside ICC profiles colours are defined by a numeric value, based on where they are in the CIE Lab or CIE XYZ colour space.
Caption: In ICC technology the reference colour space is not RGB or CMYK, but a device independent colour space, CIE Lab, as shown here. Redish colours have positive a values, yellow positive b values, greens negative a values and blues negative b values. But you don’t necessarily need to know this to use ICC profiles.
What devices do I need to calibrate?
Caption: All apps compatible with the ICC technology support both soft- and hardcopy colour accurate proofing by applying the relevant ICC profile for the printed job. Here an example from Adobe Photoshop, where the popular Fogra 30 ICC profile is used for prints made to be compliant with ISO 12647-2 (Process control for the production of half-tone colour separations, proof and production prints -- Part 2: Offset lithographic processes).
Colour accurate proofs
This can be a step too far for many designers as most prefer to do colour accurate soft proofing on screen, typically through Adobe CC and/or Adobe Acrobat. But remember, colour accurate soft proofing isn’t possible unless your monitor is calibrated and stable over time. Investing in a good monitor and learning how to calibrate it correctly is an important and necessary step for your wild format projects.
How do I do softcopy proofing?
In order to preview or soft proof your design colour accurately on your calibrated monitor, you need an additional ICC profile for the output method to be used in final production. This profile describes the output device’s colour characteristics and a colour savvy printing company can provide you with such profiles. You copy the profile(s) to the systems folder on your computer and you can now tell Adobe CC what the output CMYK colour space is and ask for a colour accurate preview on your calibrated monitor. This is what is meant by soft proofing. Artwork can still be in RGB because it’s only temporarily converted to CMYK for viewing on the monitor, showing you a colour accurate soft proof of what your work will look like in print. If you want, you can make a final conversion to CMYK at this stage, but if you change your mind about what printing technology you want to use, this conversion isn’t valid. Keep back-up copies of the RGB file if you want the flexibility to choose different print methods.
Another way to do the colour conversion is to create PDF files and to do the colour conversion automatically when the PDFs are generated. The relevant ICC profile will be embedded inside the PDF ready for the printing company.
How do I do hardcopy proofing?
Spot the difference
The ICC technology only provides good colour management for working in either RGB, CMYK or greyscale (black and white). While you can call for spot colours in your designs, they are not very well displayed, or colour managed unless you use a special application such as the tools EFI provides as part of its Color Profiler Suite. There are developments underway to improve colour management for spot colours in the latest version of ICC’s technology, but either way you must learn to properly colour manage RGB and CMYK in your processes to get the best results.
By learning about and applying ICC technology you can preview colours in your artwork as they will appear in the final print. This will help you avoid colour errors and so reduce waste and disappointments. It will also save time, expense and stress, so build up your knowledge and experience to master it and give yourself a value-added edge.
The Wild Format guides are intended to expand awareness and understanding of the craziness that can be created on wide format digital printing devices, from floors to lampshades and everything in between. These guides are made possible by a group of manufacturers working together with Digital Dots. This article is supported by Digital Dots, EFI, Fujifilm and HP.
FESPA’s new colour management feature, COLOUR L*A*B* will be introduced for the first time at Global Print Expo 2019 in Munich. It is aimed at helping visitors improve colour management practices in their own print businesses. The feature provides a walk-through showcase of representative technologies from a range of specialist suppliers, live demonstrations, guided tours of the exhibit, and educational presentations from subject matter experts. Book your tour now and discover the steps and technology to achieve consistent colour throughout your production mix.
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