Keith Martin
Tackling colour settings, profiles and calibration can leave even experienced designers quaking with fear, so here’s what you need to know…
I find that RGB vs CMYK, colour profiles and picking the right settings is a constant source of confusion for designers. This isn’t surprising; it’s a murky subject and there’s a lot of misinformation thrown back and forth. So…
Adobe RGB (1998) is the best RGB colour space to use for general work, including scanning, digital photography, and image manipulation and adjustment. It covers a broad part of the visible spectrum and can be achieved almost completely by decent-quality displays. The sRGB standard is more of a lowest common denominator colour space, one that covers the range of colour that you can reasonably expect to be achievable on the average, bog-standard display – not on a high-quality display. As I sometimes tell people, although the ‘s’ in sRGB is for ‘standard’, there’s another shorter word beginning with ‘s’ that could equally be used.
My Photoshop image fine-tuning is done in Adobe RGB. Then, for web delivery, because most browsers and browser plug-ins assume image content is sRGB (and hence produce particularly dull renderings of content that’s in a broader RGB colour space), I convert the profile to sRGB in Photoshop. (That’s Edit > Convert to Profile, not Edit > Assign Profile.) This gives me the best standard colour space for editing, and then produces the best final results in sRGB once I’m done. Of course, when I’m working for print, I don’t convert to sRGB. Ever. Bog standard, lowest common denominator, remember?
Calibration is actual adjustment of the behaviour of a device, normally a display, although it can be a printer or even, in theory, a scanner. The idea is to get the device working as best it can by calibrating it, then to profile it – using a Spyder, ColorMunki, Huey, Eye-One or similar device – to measure just how well it performs. The thing to remember about profiles is that they don’t change your image content; they just describe the characteristics of whatever device they’re for. Here’s a nutshell explanation of how this works with input, display and output devices:
A monitor profile describes the strengths and weaknesses of that monitor, and the colour management system adjusts the signal sent to that display to compensate.
A scanner profile describes the way the scanner’s results match or don’t match the original, so the colour management system also knows what compensation should be used when dealing with something with that scanner profile.
A printer profile describes how well or otherwise the printer manages to do at rendering specific colours, shades and tones, so the colour management system can take that into account when print data is compiled and sent to the device.
You can use the profile of one output device to proof something using a different output device. For example, you can use a (high-quality) inkjet printer to proof the way work will look on a four-colour offset litho press. The caveat is that you need accurate profiles for both, and that if the proofing device can’t quite render the same tones/hues that the destination device can, then the proof will be limited in those respects. This isn’t normally a problem if you proof CMYK offset print work using a good-quality inkjet printer; it should be able to render the full CMYK gamut and more. However, if you’re not sure how good the proofing device is or how accurate the profiles themselves are, watch out.
Then comes the issue of picking colour settings within your software. If you use Adobe’s Creative Suite 3 or later then select one main application to configure the colour settings. I suggest Photoshop, as it has the widest range of controls.
I don’t tend to use Adobe’s generic colour settings – they’re safe enough, but certainly not ideal for sheet-fed work on normal coated stock. My standard settings for regular printed work and all photo manipulation, when I don’t have specific press profiles to work with, are as follows:
Working spaces:
RGB Adobe RGB (1998)
CMYK Coated Fogra39 (ISO 12647-2:2004)
Gray Dot Gain 15%
Spot Dot Gain 15%
Colour management policies:
RGB, CMYK and Gray all Preserve Embedded Profiles
Description:
‘General-purpose colour settings for print. Adobe RGB and Fogra39.’
The description isn’t a technical necessity, of course, but it always helps to include some kind of memory-jogging reminder of what settings a preset actually contains. The ‘general-purpose’ term is because the true ideal is to get specific detailed output device settings from whoever will manage the prepress and print for a particular job. In the real world, this is pretty rare so, in lieu of that, Fogra39 is a reasonable fall-back standard for general offset litho work.
Fogra is a recognised European standard and a ratified ISO standard, too. I recommend this over the slightly thin results that you can get from US Web Coated (Swop), the normal defaults.
Print geek detail time: this also specifies positive (European standard) rather than negative (US standard) plate imaging processes, which will make a difference to dot gain curves if using traditional methods, although not if you go the CTP (computer to plate) route. Yes, the world of print output specifications gets more complex the harder you try to make sense of it.
Whatever you do, don’t use Euroscale. That ink standard is deprecated and has been for a number of years. You won’t see it in most lists these days, but avoid it if you do come across it. Once you’re done, save those, go to Adobe Bridge and pick your custom settings as the suite-wide synchronised colour settings. Bridge can’t configure the settings themselves, it’s only used to select which of them you use as your suite-wide colour setting defaults.
Finally, that RGB vs CMYK thing. RGB colour can be brighter and more saturated than can be achieved in CMYK, but there are a few parts of the CMYK spectrum (notably 100% cyan) that can’t be precisely rendered in RGB. Colour conversion from RGB to CMYK should be done only when you know what standard to use (for example, Fogra39, US Web, US Sheetfed, Web Coated Swop or a specific press profile). Going from RGB to CMYK throws away data that you can’t get back, so do your homework first, even if this means just picking a general standard that seems appropriate.
Do you have to convert to CMYK at all? Traditional wisdom says ‘of course’ – that’s how print works, after all. RGB has to be turned into CMYK at some point, and you should be in control of these things. However – and this is where some modern practice breaks with tradition – you can use an all-RGB workflow and have your colour converted to CMYK as late as possible in the prepress process, rather than before assembling the layout.
This can be the point of creating PDFs, and you can even generate PDFs without converting, leaving the process to the final prepress Rip stage. The thinking goes that this ensures your RGB colours are converted as appropriately as possible, but it also means you have taken your hands off the wheel (as it were) before that all-important point. If your profiles and presets are all set up just right and the final Rip stage is also well managed, the conversion will go smoothly.
Even then though, if you want to match precise CMYK colour values with utter confidence, you need to produce those yourself. So, in these cases, when working for print, specify those colours in CMYK even if your workflow is full RGB. Yes, a hybrid workflow – a bit of one and a bit of the other.
Profile your screens and printers regularly, set up your colour settings properly in the Creative Suite, and remember one thing above all else: when in any doubt, ask whoever will be handling the prepress and print end of things.
