CMYK once seemed like a given for print But with such a diversity of output devices now at the end of the workflow, a common question is whether to keep a file in its RGB format to a late stage in pre-press. Is there scope for a colour model revolution?
There’s certainly no shortage of primary material in RGB. After all, digital capture devices, down to the most basic consumer cameras and scanners, grab data in RGB. Conversion to CMYK four-colour separations ahead of platemaking is increasingly seen as a hangover from analogue pre-press days – but is still regarded as a viable process if the destination device is an offset or digital production press.
But the new generation of wide-format inkjet printers often have additional colours, such as orange, and are capable of producing a far more ‘hi-fi’ image than what is supplied in a CMYK file.
“It all depends on what kind of device the material will be printed on,” says Agfa commercial print products manager Harry Kontogiannis.
“These days, with so much print being multi-purposed to offset, digital, and to electronic destinations such as plasma screens, or the internet, it pays to consider the destination before making the call on RGB or CMYK.”
One-way street
The point is that CMYK has a very restricted colour gamut, so once the image or artwork has been converted from RGB to CMYK, a ‘one-way street’ has been walked, with no recourse to undoing things.
“When you convert to CMYK, you shed a lot of data and shrink the colour space. That’s not an issue when you’re making plates for a press, but if you are intending the job to go to, say, a wide-format inkjet device, you’ve lost a lot of data that these devices are capable of,” explains Kontogiannis
So what is an RGB workflow? It means leaving a file in its RGB format until the last possible stage, and then converting it to CMYK in the RIP.
There are also several intermediate points where conversion can be made. However, today’s widely accepted PDF-X-1A platform is designed for CMYK and may even reject or “re-fry” files that do
not conform during pre-flighting. As such, the newer PDF-X-4 platform is a more tolerant vehicle, suggests Kontogiannis, but is not in common usage in Australia, at least not yet.
RGB-friendly software is available. For example, Adobe Creative Suite will honour the RGB format and Acrobat will PDF it as RGB. And with today’s workflow products from the major pre
-press vendors, conversion has a ‘drag-and-drop’ simplicity.
“But a prerequisite for working in an RGB workflow is an excellent understanding of colour management,” says Kontogiannis. “The operator needs to get the right RGB profile to the RIP software to maximise the quality.”
Many press operators are used to a certain type of colour separation and, when faced with working in RGB, may not be familiar with rendering ICC profiles in grey component replacement (GCR) or under colour removal (UCR).
“This could have diabolical consequences,” warns Kontogiannis. As a rule of thumb, Australia’s pre-press departments are still “around 80%” supportive of CMYK workflows. “There’s a lot of voodoo out there about colour management, so printers like to stick to what they know.”
Why not CIELAB?
Heidelberg ANZ’s product manager for pre-press and workflow, Soeren Lange, asks why files are not kept in the ultra-large CIELAB format, which has a larger colour gamut than the largest of the RGB format types.
Working in large colour spaces such as CIELAB enables the user to take advantage of proofers with a wide colour gamut from manufacturers such as Epson and HP, as there is more colour information in the file before converting into a smaller space like RGB or CMYK. Down-conversion should be left to the last possible point, either in the RIP or using Heidelberg’s colour tools, he says.
“If you only have the choice between RGB and CMYK, I would always recommend RGB. But you could also leave it in CIELAB and just attach the colour profiles for the monitors, which should
be calibrated anyway.”
Lange says the tendency, deeply ingrained, to convert down to CMYK sometimes originates at the very point of image capture. Photographers know their work will be used in four-colour print, so some will helpfully decide to convert their files down. That same mindset exists in agencies – so that by the time the artwork arrives in pre-press, hi-fi colour options are foreclosed.
Lange says that education facilities such as the International Centre for Graphic Technology at RMIT, as well as the trade press, as agents for change on this issue.
McKellar opts for RGB
One printer that has got behind RGB workflows is McKellar Renown in Melbourne. Managing director Stephen Norgate blames the tight economy and risk-averse thinking for clients’ file submission habits. Mistakes cost money, and everyone is playing it safe.
The all-offset commercial printer produces high-end mail-order catalogue work, where images of fashion products are the customer’s only access to the merchandise, so it has to be totally accurate, says Norgate.
He estimates that in around five years, the industry will be more attuned to the colour needs of printing, and will stop trying to make ill-advised conversions to CMYK before submitting files.
“At present, photographers or their assistants, or the designers that end up with the files, think that because the destination is print, they need to make their own file conversions, but Photoshop isn’t the best way to do that.”
Armed with dedicated Heidelberg colour management software, McKellar Renown’s own pre-press department is in a much better position to make quality conversions. McKellar Renown’s business development manager Zoran Ovuka describes the subtractive CMYK separation as “three colours and black, trying to represent a complex image on white stock – it’s not going to be nearly
as true as RGB”.
Another RGB advocate is The Digital Centre. The company, which has around a dozen staff, is based in Sydney and produces ongoing work for many of Australia’s top agencies. Production director Ashley Risstrom relies on years of exposure he has gained through being a production/operations manager building business workflows from the ground up, in magazine, agency, financial and capital markets.
He has considerable experience in commissioning an array of web offset, sheetfed and digital print to meet end-clients’ expectations.
Risstrom says the type of workflow used depends on the job. “If I’m briefed on a job where visual impact is paramount, I’ll guide them into an RGB workflow.” This takes full advantage of the additional colour gamut available in digital print.
To obtain the most out of this technology, conversion to CMYK takes place either in a colour management server, profiled to individual devices, or converted in the output device’s RIP itself.
Even when the file is finally converted to CMYK, a late conversion before platemaking is going to create a much more detailed, nuanced image, than receiving the file in CMYK, he says.
Lack of knowledge
Risstrom confirms a lack of knowledge upstream in the industry at large – and calls for a review of processes at the designers’ studio. A common complaint is inappropriate files submitted for print.
For example, photo files that have been used for web printing a catalogue are reissued for a offset-printed campaign or even for optical media. “The bottom line is that the end-user is not always gaining the visual impact available for each of these technologies,” says Risstrom.
“The policy should be ‘build once, repurpose infinitely’. The gain you get from that is that you maximise productivity and consistency,” he adds.
“They had the right idea in the good old says, maintaining one ‘master trannie’.
“The way the industry worked in the past was a master trannie was built by the photographer or agency. This included retouching, cropping, colour correction, and so on. The master trannie was then issued to pre-press houses to scan appropriately, based upon the printing method. This workflow was RGB scanning, then processing into CMYK separations at the last point prior to
film being made.”
Colour accuracy and repeatability are the basis of good colour management, argues David Crowther, technical manager for DES, who heads up the company’s colour training division, Chromaticity Australia.
“There’s not much point achieving a special colour in a wider RGB space, if the client needs print that conforms to a CMYK proof within an ISO colour space and needs to match previous work. CMYK is more predictable for this. But where special colours can be of value is for spot applications, such as corporate colours or specialised packaging.”
Crowther says printers have tended to stay in their “CMYK comfort zone” and this determines the workflow. Converting to CMYK on a CTP RIP just before plating – in order to preserve the RGB space – may sound fine in theory. But finding out there are mistakes when you are on the press can be expensive.
A client will want to see a CMYK proof that matches the CMYK outcome from the plate, or even a CMYK rendition on a monitor if the job is going to be proofed remotely.
RGB workflow: Pros and Cons
PROS
With so much print being multi-purposed to offset, digital, and to electronic destinations, an RGB workflow preserves the image files at a superior quality to CMYK.
The RGB format allows digital proofing and printing devices that can produce special colours to use hexachrome inks to their full advantage in a much wider colour gamut.
CONS
CMYK offers repeatability and consistency, even if that’s at the expense of more vibrant hues in a wider gamut.
Conversion to CMYK is a familiar and trusted process. It meets ad agencies’ expectations for print.
Press operators are used to a certain type of colour separation and, when faced with working in
RGB, may not be familiar with rendering ICC profiles in grey component replace-ment (GCR) or under colour removal (UCR)
Case study: SOS Printing
Michael Schulz, managing director of Sydney-based commercial offset and digital business SOS Printing, sees the RGB-CMYK debate as a cultural change. “For years, we’ve been telling our customers to submit everything in CMYK, but now we’re realising that staying in RGB as long as possible would give us enormous benefits, in terms of colour gamut and range.
“So now, when we get files in RGB, we colour-correct them in that mode and then change them to CMYK at the RIP stage. But we still tell most of our clients to give us files in CMYK because we’re used to that and for a long time we’ve trained to do that,” he says.
Working in RGB has benefits for offset as well as digital printing, he says. The 32-year-old company, which has around 120 staff in Sydney and 50 in Brisbane, and an annual turnover around $37m, prints on Heidelberg Speedmasters, augmented by Kodak and Océ machines, alongside a Xeikon 5000.
Schulz says the company is starting to realise that colour gamut-enhancing presses, such as Xeikon and Kodak NexPress, can make the most of the extra information in RGB. “It’s only a matter of time before everything should remain in RGB as far downstream as possible.”
“When you colour correct in RGB, it gives you more to play with, and you convert when you know what kind of output you’ll have. For one of our digital presses, we’d get more vibrant colours in RGB. By converting to CMYK, you’re ‘dumbing down’ the file, and the earlier you do that, the more data you lose,” he says.
“For some printers, that’s a good way to operate, because their logic goes that if the customer has already killed the file, they can’t be blamed. But it’s not in the best interests of colour management,” explains Schulz.
“Nowadays, pre-press people don’t care so much about CMYK, as it’s not so print-oriented. They work in RGB on their monitors, and they want to be able to print what they see on screen.”
But Schulz says a good RGB workflow depends on customers’ screens being calibrated. He explains they must have an SOS press profile loaded in Acrobat. The company is undergoing ISO certification through Kayell, and Schulz says he is looking forward to more accurate levels of colour management between clients and his pressroom.
Some customers are agnostics, says Schulz. “They have no idea. They feel the printer should do the tricky stuff, so we just say give us your files in RGB.” Schulz sees an RGB workflow as a product of an age in which designers are looking beyond print as their output medium and, moreover, do not have much knowledge of how print is processed.
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