What makes colour tick
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By Sophie Matthews-Paul
19 July 2012
Dr Gabriel Marcu understands his colour principles inside out and is eager to share his knowledge (pic: IMI Europe)
Colour is a funny thing. It affects our lives in every waking moment (and our dreams), and determines the way we gauge our responses to everything surrounding us. Yet although it comes as a by-product of the light spectrum, is received by our eyes and processed by our brain, we tend to take it very much for granted in our daily work. Many of those involved in its reproduction in a printed product often fail to observe its relevance on display and output devices, yet we depend on its fidelity throughout the applications we produce from photographic prints through to wide-format graphics.
IMI Europe's recent course on colour and colour management wasn't for the faint-hearted as it provided some very in-depth explanations, ranging from fundamentals, through coding and principles, to the essentials of gamut mapping and quality factors. The sessions were taken by Dr Gabriel Marcu, senior scientist, Colorsync Group at Apple. His in-depth experience of developing practical methodology on all things colour is based primarily on the characterisation, calibration and tuning of digital devices, such as displays and cameras. And he's designed and programmed applications for analysis, 3D visualisation of colour spaces, half-toning and gamut mapping.
The focus of this course rested on the primary elements needed for colour reproduction in display and print devices, with considerable concentration on the roles played by measurement, computation and interpretation of data. As well as these principles, we also observed more familiar half-toning techniques, and the unwanted effects of dot gain on black and white and colour examples.
What did I learn? Firstly, we all discovered how our eyes and brains can play tricks on us when we look at colours and the relationships they have with one another. We looked at examples which demonstrated constancy and the effect of different illuminants, and how complex interactions can produce strange and unexpected results for the viewer. It doesn't help, of course, that colour itself is a matter for subjective interpretation, and none of us really knows how others see the same shade.
From there we moved onto more heavyweight topics, touching on absolute and perceptual spaces, and the relevance of device dependent and independent colour. Then we covered the importance of being able to transfer and communicate colour reliably between devices, the difference between analytical and empirical models, and how to determine accuracy and data measurement.
Along with highly detailed explanations relating to gamut mapping, colour management and viewing conditions, we also spent time considering the performance of profiles and how to apply them. This took into account that, for print devices, this is considerably more complicated than it is for a display not least because individual materials have to be taken into account.
So how is all this relevant to wide-format digital print? The concentration on what colour actually represents goes a long way to providing a general understanding about its principles and what affects it in our everyday lives. Knitting our perception of colour with a digital remit of how it should be represented is valuable fodder when considering how to reproduce it in a consistent and accurate manner, with control and management being essential prerequisites to ensuring precision across a variety of devices. Adding greater knowledge about the application of colour principles to different models, and not just those we associate with the reproduction of CMYK, provides a broader understanding of the relationships between additive and subtractive mixing.
Most of us can probably muddle through satisfactorily without knowing why colour reacts to different algorithms that can affect its end reproduction, but any information we can glean along the way can be valuable as well as memorable. What the use of sensible management boils down to is how that can be assigned to different needs and models, taking into account external influences, such as luminance, media and output device. We tend to work in environments where we have the tools that automate most of the procedures, with minimal human intervention. This means that calibration, linearisation of our printers and the building of the correct ICC profiles are not left up to the eye of an individual in order to get it right.
Marcu's enthusiasm for his subject is infectious, encouraging you to soak up information. He has certainly made me spend a little more time considering how it influences everything I look at, from computer screen to everyday objects, and assess the relationship of colour with everything that surrounds it, whether it's in our natural surroundings or computer generated and driven.
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