Print Technologies: Color Management

Pantone Hexachrome

Based on the modern and evolving technology of the Net, it's no real surprise to see such major developments and general upheaval. In the long-established and generally conservative world of commercial print, meanwhile, it is often difficult to imagine how things could even begin to change. Just such a shake-up will happen, however, if a new colour printing technology lives up to its potential.

I'll come on to this new system later, but first let's take stock of the current situation regarding colour printing. It's not a pretty picture. Those users new to publishing naturally expect to be able to select a colour on screen and then get matching output from their desktop printer and from their final commercial print-run. As anyone who has ever produced a printed publication knows this is very rarely the case. Even with the latest technology, and expensive Chromalin proofs, there is always a feeling of trepidation when it comes to seeing how the colours you chose actually turned out.

To understand why accurate colour printing is just such a nightmare it is important to recognise the fundamental difference between the two main colour printing models; solid and process. Solid colour printing is based on the use of a different ink for each colour used, while process colour printing is based on creating multiple colours by combining the four base inks, Cyan, Magenta, Yellow and blacK (the so called CMYK system).
Spot Colour

The main reason for using solid colours is that it is considerably cheaper when you are only printing two or three colours - which in practice normally means black and one or two other colours. This means that solid or spot colour printing is the most common form of commercial printing for the majority of individual and corporate publications ranging from business cards to menus, posters to stationery.

For many of these jobs such as two colour posters, the precise colour used isn't too crucial. So long it comes out as a strong red rather than a pink or a purple the customer's not too concerned about the particular shade. For corporate work however the demands are very different. When another batch of letterheads are printed, they must still match the existing continuation sheets and compliment slips. Above all else, colours must be accurate and consistent.
The Pantone Spot Colour Solution

Thirty years ago colour matching like this was pretty much a matter of chance. You would give the printer a sample and they would have to use all their skills to come up with a comparable ink and then, more often than not, to come up with a convincing excuse for why it was impossible. Things changed in 1963 when Pantone Inc introduced their colour matching system. Through their Formula Guide, designers were offered a set of 942 specific colour swatches each with their own numeric identification. Armed with this Pantone number, the printer could then accurately recreate the colour by mixing the fixed proportions of Pantone's own proprietary seven ink set.

The improvements the new system made to colour accuracy and consistency were so huge that nowadays spot colour printing is more or less synonymous with the name Pantone. Any business with corporate colours will know their Pantone references and any self-respecting designer will have their own Pantone guide. In fact, because the colours depend on the paper they are printed on, most designers will have the guides on both coated and uncoated stock - though few are likely to follow the recommendation of buying fresh copies each year to avoid the effects of fading.

For those who do a lot of two and three colour work there are further Pantone guides to help take the guesswork out of colour specification and to make the most out of a limited budget. The Colour Tint Selector is particularly useful for specifying hard-to-visualise halftone tints for each of the Pantone colours, while the Colour and Black selector shows different combinations of tints of 240 selected colours with tints of black. The Two Colour selector does a similar job for the same selection of 240 colours combined with each other. Finally the Black Colours and Effects guide tries to make the point that even the colour black can be made a design feature, though this is the one book it would be very easy to live without.
CMY(K)

As the advanced Pantone guides shows there is an amazing range of effects that can be created with the combination of two inks, but this pales in comparison to the possibilities offered by combining the four process colours. By combining different percentages of the process inks - cyan, yellow, magenta and black - it is possible to create the whole rainbow of colours from red to green to blue. In fact, strictly speaking, there are only three process colours - cyan, yellow and magenta - as together solid versions of these colours will produce the fourth, black. In practice, however, as the black produced in this way would seem slightly brown and would need amazingly tight registration of plates to work for body text, a separate black component is also always used.

The real beauty of process printing over solid colour is that it can produce the continuous tones needed for reproducing colour photographs. This is the printing process behind any full colour publication from sales brochures to packaging to fashionable glossy magazines like PC Pro. If you take a magnifying glass to a photograph in any of these you will see that what seems like solid colour is actually made up of screens of tiny coloured dots of the process inks printed at angles to each other to produce the colour effect.

The fact that colour photographs can be reproduced gives the impression that process printing can create any given colour. This is absolutely not the case. Because there are actually only three inks being used for colour and because of the inaccuracies inherent in the press there are only around 100,000 possible distinct shades. To accurately mimic distinct solid colours, a more realistic increment in each process colour is 5% and Pantone provide another Process guide showing 3,000 of these practical variations.

If everyone stuck to these colours that can be produced by the process inks, things would be fine, but this is where things start to fall apart. Naturally enough, some of the most common colours that you will want to produce are those from the Pantone solid standard. When it comes to print the full colour annual report you'll still want to accurately reproduce the corporate logo and make use of the corporate colours. In fact, unless you've chosen your Pantone solid colours carefully, the chances are that you won't be able to find a match. Incredibly, less than half of the solid colour standard can be reproduced on a process press!

The implications of this mismatch between the two major printing processes are enormous. In some areas of the spectrum such as the vivid purples and the vivid oranges there are no colours that come even close. If you've designed a 3 colour logo for a customer using these colours, printing a letterhead will be fine, but when it comes to a full colour brochure you're going to have explain why their purple has come out as burgundy and their orange as peach.

In fact, if necessary, you can work around the problem by combining the process colours with additional "bump" plates for the solid colours, though this will naturally be more expensive and will often involve exhorbitant retouching of plates. Much more sensible is to avoid the problem in the first place and to do this you will need yet another Pantone book, the Solid to Process guide. This shows each of the solid Pantones next to their nearest process simulation so you can stick to those colours with a good equivalent. In a way I'm surprised that Pantone haven't brought out another guide showing only these colours, but as there would be less than 500 I'm guessing that they must be too embarrassed.
On The Computer

The situation between the differing solid and process colour spaces is bad enough, but nowadays there is a whole new level of complication introduced by the computer. Colour on the computer monitor is created in a completely different way to colour on the page. Inks absorb light in a subtractive process so that 100% cyan, magenta and yellow combine to produce black. Light on the other hand is additive so that 100% of the three primary colours of Red, Green and Blue (RGB) combine to produce white.

Not only is there no direct correlation between the same colours in the two systems, the two colour ranges are entirely different. As 24-bit displays can work with 256 levels of each colour, RGB monitors can display 256 x 256 x 256 ie 16.7 million colours. With so many colours available, again the temptation is to think that monitors can produce any colour. Again this is not the case. Not only is it possible to choose colours on screen that are not printable on CMYK devices, but there are also colours that can be printed which cannot be shown on screen.

All in all it would be hard to contrive a messier system with no real connection between the 16 million RGB shades, 100,000 working CMYK colours and the 1,000 Pantone solid colours. What is needed is a standard that can encompass all three colour spaces and simultaneously provide range, consistency and accuracy. Attempts have been made in the past to provide this so-called HiFi colour but by demanding up to eight component inks they proved prohibitively expensive and, with no clear support, they have ended up as niche products.
Hexachrome

Now this is set to change as the industry leader Pantone attempts to bring in its own new system, Hexachrome. As its name suggests, the main difference behind Hexachrome is that it uses six inks. This vastly increases the range of colours the system can produce as shown in the accompanying diagram. Not only does the new Hexachrome spectrum embrace the existing CMYK gamut, it also exceeds the colour range of RGB displays in all but one minute area. It's impossible to show on the graph, but the support for solid Pantones also doubles from the current miserable 45% offered by CMYK to a near respectable 90%. As the Hexachrome press release puts it "if you can conceive it, you can achieve it".

What this means in practice is stunning quality photographs and a whole range of colours you didn't realise were missing from traditional printed material, but suddenly hit you when you see them. Striking colours like turquoise and acid green but also much more subtle pastels and nuances of skin tone. It's difficult to describe the difference, but you might well have seen an example in your local bookshop. The cover to Irvine Welsh's Ecstasy - the one with a brightly painted purple and yellow bald head - was printed with Hexachrome. If you've seen it, you'll remember it and that's the point: good colour sells.

For products like magazines and packaging that depend on customers being enticed into picking them up, the subliminal edge that colour can give them is worth a great deal. The real strength of Hexachrome however is that it will be a practical, and therefore comparatively inexpensive, solution. In particular, because Hexachrome only demands six inks, it can be printed on the thousands of existing six colour presses that were previously needed to provide the bump plates necessary for combined process and solid printing. Further savings come from the lower grade paper that can be used while still producing extraordinary quality.

More importantly, the Hexachrome system is actually based on enhanced versions of the existing four CMYK inks together with a new orange and green. For the designer the continuation of the old system means that CMYK-separated photographs can still be used together with enhanced solid Hexachrome colours. For the printer it means that it will be possible to mix Hexachrome and traditional jobs with minimal press reconfiguration. The move to Hexachrome can be evolutionary rather than revolutionary.

So how can you begin using Hexachrome? First of all, of course, you will have to get hold of the Pantone Hexachrome guide to have a reference on paper. On the computer, so far the only DTP program to support the new standard is PageMaker 6.0 though this will soon change. To access the new Hexachrome set within PageMaker, choose the Define New Colour command and select from the process libraries. If you apply any of the 2,000 colours to a page element, when you come to output the separations you will see the addition of the green and orange inks to Hexachrome versions of the normal CMYK.

To get the real benefit of Hexachrome, however, you will want to use the process for continuous tone photographs. Because the Hexachrome colour gamut embraces not only the CMYK but also the RGB ranges this means that it will no longer be necessary to convert RGB scans to the more limited CMYK. As well as the improvement in quality this will lead to quicker processing as there will be 25% less data to deal with until the very end of the production cycle. Eventually this full separation support of images should be built-in to all leading packages, but at the moment the only option is through the Hexwrench plug-in for Photoshop or through Hexachrome service providers.

Of course Hexachrome is not perfect. The costs involved with a six colour process are always going to be higher than with the ubiquitous four, and ten percent of the Pantone solids still remain stubbornly out of the Hexachrome range. More significantly, accurate proofing of Hexachrome publications on the desktop will be impossible until six colour desktop printers come into being. And we're all going to need yet another batch of guides from Pantone showing Hexachrome equivalents to their existing Solid and Process standards!

Having said this, and recognising that the system is something of a botch, Pantone must be given a great deal of credit for almost achieving the impossible. To create a practical system that unites the three colour spaces of the RGB monitor, the CMYK press and their own solid colour inks is no mean achievement. An open standard would have been preferable and helped to speed acceptance, but any system that offers up to 50% more colour than conventional print processes deserves to be a success. The acid test is that once you've seen Hexachrome in action you'll want to use it. To begin with the costs and inconvenience will limit the take-up to high-end colour publications and packaging, but over time this should lead to lower prices and a filter-down effect that will spread the system throughout the world of colour printing.
Colour Matching On The Desktop Boxout

The Hexachrome system is undoubtedly a big advance for high-end colour printing and for the future, but in the meantime we have to try and make the best we can of the existing CMYK-RBG-Pantone mismatch. This is particularly the case for the desktop set-ups used to proof work going out for commercial print. There are two main problems. The first is that although all top-end applications claim Pantone support, in fact they implement it in very different ways. The second is that although most desktop printers are based on CMYK, in fact they all use slightly differing inks and systems.

As a result, if you try specifying the same Pantone in XPress and in Illustrator for example, the two will almost certainly look very different on screen and on paper and neither will look like the actual colour as shown in the Pantone guide. I did a bit of investigative work on this and found that the most accurate applications were PageMaker and Photoshop and far and away the biggest failure was Corel Draw whose Pantone approximations didn't even come close. As this might be down to my particular set-up I can't really make any generalisations, but it is worth trying out your own system.

What this can lead to in practice is the gruesomely embarrassing situation of having to explain to a customer that the solid colour in the final run will actually look the same in both the poster produced with Corel Draw and the brochure produced with PageMaker, but that neither will look like the colour in your roughs. This has happened to me so often now that, for proofing purposes, I end up finding the nearest CMYK specification from the Solid to Process guide and creating my own customised CMYK equivalent.

A new alternative to this workaround is to use Pantone's new ColorDrive software (reviewed issue 24). This works as a central clearing house for colour, creating palettes for each of the Pantone solid and process systems - including Hexachrome - that are individually calibrated to your monitor and to your desktop printer. It's quite an effort as each application has its idiosyncracies and some, such as Photoshop, do not import names, but for serious designers it's well worth the effort. If all goes well, the end result will be that if you apply the same Pantone in multiple applications they will finally print out as the same colour. They might not be accurate, that ultimately depends on the quality of your printer, but at least they will look the same which is at least a small step forward.