Like the most reliable colour-management solutions, CPX is built on ICC technology (See “International colour organizations”), which has made it possible to standardize colour spaces (See “Colour spaces explained”) across a digital workflow. CPX profiles are incorporated into the workflow using Apple’s ColorSync, in tandem with the colour-profile preferences of applications such as Adobe’s Photoshop, Illustrator and InDesign. At present, there are problems with QuarkXPress – but more of that later. Digital workflows are only as good as their weakest link – and this is usually the monitor. The same image on the same make of monitor in the same office can look wildly different from screen to screen. Sensibly, CPX makes this its starting point. Armed with the reference print and identical RGB file, you can calibrate a monitor using the Adobe Gamma control panel. This generates an ICC profile for the screen. As with all monitor calibrations, it’s advisable to view the reference image from within a daylight box. This neutralizes shifting light-conditions caused by time of day and desk position. Every serious graphics environment should have one. They cost about £400.But CPX comes into its own with its CMYK profiles. In theory, any colour-management system, such as ColorSync, should allow you to accurately display on-screen what you can expect to see in print. However, RGB and CMYK colours are at opposite ends of the colour spectrum, and are displayed and lightened in very different ways. On a monitor, one lightens colours by adding light; yet on paper, this is done by subtracting ink. This difference accounts for most post-press let-downs. Because of this, CPX’s CMYK profiles are tailored for specific print-job requirements. There are three newsprint profiles, three offset profiles, and one for Gravure (used for huge print runs, where images are etched on the print cylinder). These CMYK profiles make allowances for dot-gain (how readily ink soaks into the paper) and total ink coverage (the total ink saturation of a print job). In newsprint, dot-gain is high, because paper quality is poor. But for offset jobs that use coated paper, it’s much lower. Conversely, ink coverage in newsprint is lower, but for offset jobs it’s much higher. To select the correct CMYK preference, call your printer and ask what the dot gain and total-ink coverage is for the paper stock used to print your newspaper, magazine, poster or calendar. Then consult the CMYK-profiles overviews in the CPX manual and select accordingly. For Macworld, the correct CMYK preference was Offset B. This profile is designed for use with a coated paper-stock of between 110-170g, a total ink coverage of 335 per cent, and a dot gain of between 8-12 per cent. The profiles also carry information about colour separations in both UCR (undercolour removal) and GCR (grey-component replacement). UCR involves the replacement of some of the CMY component of neutral colours with an equivalent density of black, to reduce ink usage and improve reproduction. GCR performs a similar function, but works in colours as well as neutrals to replace CMY with black. Baptism of fire
But does it work? The only way to test CPX was to use it on last month’s issue of Macworld, compare the printed pages against their onscreen equivalents – and pray. I’m happy to report that the RGB pages and the printed versions were as close in colour as damn it. I also ran a similar test using the previous issue of Macworld, which was output – as all earlier issues were – using generic RGB and Euroscale Coated CMYK. Here, there was little resemblance between screen image and printed page. Yet, when I selected the CPX RGB and CMYK colour profiles for the same pages they transformed before my eyes into reflections of their printed counterparts. Another boon with CPX is that it doesn’t matter if external artwork is embedded with wildly different colour profiles – because what you see on-screen is still what you’ll get in print. This is because the CPX profiles show you how an image will print on your paper stock, whatever its embedded profiles. For example, in this issue of Macworld, we received an image from a freelancer that came in with a SWOPcoated CMYK profile. SWOPcoated is the default US colour profile, and contains about 4 per cent more magenta than the Euroscale profile used over here, and which gives less saturated skin tones. Photoshop and Illustrator are the natural homes for CPX profiles. This is because they are bespoke graphics programs and are driven by powerful colour-engines. You select the CPX colour profiles in these apps’ colour preference dialog boxes, and that’s about it. Unfortunately, as with all colour-management solutions, CPX is hamstrung by the disharmony between the Mac OS and the leading software houses. We experienced a problem with CPX in Photoshop 5.0, where CMYK TIFFs refused to open. This, says CPX, is due to a clash with Mac OS 9.0.4. The suggested fix is to upgrade to Photoshop 5.5 or 6.0. So, what about XPress? It’s bad practice to use the XPress colour-engine for any colour-management system. This is because it’s a layout tool, and its colour engine is feeble compared to that in Photoshop. CPX is still in the testing phase with QuarkXPress. To my horror, though, I learned all this only after sending a third of the magazine off with the CPX profiles embedded in XPress, instead of Photoshop. By all means colour-preview pages in XPress (by selecting the CPX profiles in the Colour Preferences dialog box), but make sure you uncheck Colour Management Active before sending pages. This gives you the WYSIWYG accuracy without the risks. In the end, of course, colour management is fine and dandy – but any system can come a cropper once your plates are sitting on the Heidelberg. If the person operating the press has a stinking hangover, then pages may look crap whatever you do. And of course, on most magazines – including Macworld – the colour accuracy of ads takes presidence over editorial. Most of our ads are supplied as film, containing who knows what profiles. If the printer decides to tweak-up the magenta on an ad to improve it, then the colour consistency on editorial pages will suffer. Unless CPX becomes the print-industry standard, there’s little you can do about this.
Colour management can make your head ache and eyes water – especially when cost is mentioned. However, CPX comes as close to the Holy Grail of WYSIWIYG as I’ve seen. Using paper-stock-based profiles makes perfect sense in theory – and practice. All this for £575? You can’t really go wrong.