Colour management needn’t be something best-left to others. Understanding how to create a colour-accurate workflow will benefit you, and your clients.
For many designers, colour management represents one of those laborious, best-left-to-later chores on a par with sorting your sock drawer or cataloguing your CD collection. You know you should do it, and the benefits are vaguely obvious, but in the hectic, day-to-day up-against-it design studio, it’s often way down the To Do list.
Yet colour management in today’s modern studio is vital. With a huge rise in the number of devices used to capture colour – from hundreds of digital cameras, film and drum scanners, to a raft of flatbeds – and a subsequent rise in the tools available to edit colour, the need for consistent colour is paramount.
Couple this with a giddying array of output devices – from offset printing presses to humble inkjet printers – and the chances of outputting an image that enjoys a close colour fidelity with the original, captured-image is more open to chance than should be acceptable in a professional studio.
To compound this, colour management seems a complex process, on the surface at least. While most designers understand the need to ensure that colour information translates accurately between devices, as soon as acronyms such as LAB, CIE, ICC are called into play, or colour profiles discussed, many designers with deadlines looming would be forgiven for tuning out.
Yet, with a bit of effort – and a spare couple of hours – it should be possible to establish a colour-managed workflow that benefits both you and your clients in terms of created colour-accurate output. The results are worth the effort.
By ensuring that colours are displayed and printed as close to the original as possible, you can avoid unexpected colour-shifts when projects arrive back from commercial printing – and angry clients who then refuse to pay up. A colour managed workflow makes good business sense. Before delving into the practicalities of establishing a colour-managed workflow, a basic grasp of how colour is handled will stand you in good stead.
Easy as RGB
A typical studio will capture, edit, and output colour in a variety of ways. The problem is that each device, such as a scanner, digital camera, or monitor, interprets colour differently to each other – even devices from the same manufacturer will handle colour differently – and the reason is that each device operates a different colour space, or gamut. And that means that the devices simply aren’t able to display the same colours.
RGB devices, such as monitors, are brilliant at displaying Red, Green, and Blue colours due to how they project light onto a dark surface. Printers, on the other hand, are excellent are reproducing Cyan, Magenta, Yellow, and Black (CMYK), since they use inks with these pure colours.
However, a printer can only reproduce the colour blue by mixing magenta and cyan ink – which can’t possibly render a blue as bright and clear as that seen on a monitor. These colour spaces are ring-fenced areas with a set amount of colours that can be reproduced.
The human eye, for example, can see billions of colours. RGB displays can show only a limited range of these colours, while the CMYK gamut can show even less. This becomes an issue when a colour shown in the RGB colour space is outside the area of possible colours that CMYK can handle. That colour either needs to be remapped to its closest CMYK equivalent, or clipped off.
While this is unavoidable, the real issue for designers is thinking that colours seen in RGB will all accurately output identically in CMYK. What is needed is a way to alter the RGB image so it gives better representation of the final CMYK output.
The language of colour
You can think of colour spaces as different languages, and colour management as translation dictionaries. Each device in your workflow speaks a different colour language and, with so many languages, a standard international language was created – much like Esperanto – for translating colour.
In a nutshell, this international language would need to be able to display every colour possible, so that colour captured by any device (in any colour language) could be translated into it, and then a second device could take that translation and reinterpret it for its colour space, or colour language.
This international language was established in 1931 by the Commission Internationale d’Eclariage (CIE). It devised a three-dimensional representation of colour based on the theory that a colour cannot be both red and green, nor be both blue and yellow at the same time.
By using positive (+) values to represent red and yellow, and negative (-) values to represent green and red, and by adding a lightness value, a massive colour gamut was created, called
LAB (where L = lightness, A = red/green, and B = yellow/blue).
What this means is that all professional devices and software that handles colour can convert its individual colour language to LAB (from, say RGB), edit it, and then transform it back from LAB into, say CMYK. The amount of translation – or colour adjustment – required for each device is defined by an ICC colour profile, created by an independent calibration program.
To create a colour-managed workflow, you need to create an ICC colour profile for every device in the chain – from digital cameras, through monitors, to printers. Usually, these are generic profiles supplied by the manufacturer, or you can roll your own. For scanners, you’ll need to scan an IT8 test target – basically, a standardised image showing the complete range of colours – and process the file with your profiling software, which in turn creates a lookup table to convert the RGB images captured by the scanner into LAB.
For monitors, a series of colour patches are usually shown in sequence on screen, which are then measured with a device known as a colorimeter, or spectraphotometer, which in turn creates a table that takes the translated LAB values from the input device (the scanner) and translates them into the RGB space of the monitor.
Finally, the output device, such as a printer, needs to print a set of standard colour patches, which are then analysed with a spectraphotometer to create an RGB or CMYK table that draws from the LAB values created by the input device and editing software.
Practical colour magic
That’s the theory, luckily the practice is a little easier. With monitors, you have two routes – calibrate by eye, or calibrate with a dedicated device. While it’s possible to make a decent fist of it with visual calibration with software utilities such as Adobe Gamma, there really is no substitute for a good hardware colour calibration suite, such as Digital Light & Color’s Profile Mechanic.
These operate automatically, clipping onto the screen and reading a series of patches, and generating a profile. To choose a calibrated profile differs according to computer platform. With Mac OS X, choose the profile from System Preferences > Display and select the Colour tab.
In Windows XP, choose Desktop > Properties > Settings > Advanced > Colour Management and activate the profile. It’s also worth ensuring that your monitor’s White Point is set to 6500 Kelvin, and Gamma to 2.2 on Windows. With Apple monitors, set the Gamma to 1.8, or 2.2 for LCDs.
While all scanner calibration software differs, the principles remain the same, and most scanner software will feature a colour management option that allows you to set input, RGB, and CMYK profiles. The input profile is also called a source profile, and should be the one supplied with the scanner.
The RGB profile selection should be the one that is identical to the colour space you’re using in Adobe Photoshop (see boxout), such as sRGB (which has a gamut suitable for on-screen work) or Adobe RGB 1998, which is more suitable for work that will eventually be printed. The same applies for the CMYK setting.
Our thanks to ColourPeople for parts of this article www.colourpeople.co.uk.