RIP introducing CMY into grey when grey only contains K

[nawest]

We have created literally thousands of pieces of artwork in Indesign that have been exported as PDF and sent to various large format printers over many years. Recently it came to light that one of the PDFs containing tints of black had printed 'brown' by introducing cyan, magneta and yellow into the mix. The InDesign file showed as pure black, the exported PDF only showed pure black, but CM and Y were printed in addition to the black.

On the face of it, because the PDF shows no cyan, magenta or yellow in the grey, the blame would be placed on the RIP, but is this the case? Is it possible to create a PDF that shows one CMYK mix but prints another?

Indesign is set to CMYK, synched to Europe General Purpose 3,
PDF 1.6, PDF/X-4:2010, no colour conversion. Intent profile: document CMYK coated FOGRA39

[Eugene Tyson · Accepted solution]

If the printer’s RIP is using a different colour profile than the one embedded in your PDF, it can convert your pure K tints into a 4-colour black during processing. That’s one of the most common reasons a clean K-only grey suddenly turns into a CMYK mix on press.

Another possibility is that someone at their end opened the PDF in Illustrator or another application not intended for editing PDFs. Illustrator in particular can reinterpret colour spaces or introduce unwanted colour conversions when a PDF is forced into its native editing model.

But the key point is this:
Your InDesign file shows pure K, and your exported PDF shows pure K in the separations. That means the CMY was introduced after the file left you.

Any competent printer should have checked separations at the RIP stage. Seeing four plates for elements that are supposed to be black-only should have been an immediate red flag. The fact that this wasn’t caught suggests:

• They ran it digitally and their RIP forced a rich black / composite build, or

• It was gang printed with no individual colour management, meaning “whatever comes out, comes out,” and they didn’t take the time to ensure the greys were running as K-only.

If the supplied PDF contains only K, and the output shows CMY, then the issue lies entirely with their workflow or RIP settings not your artwork. You’re not responsible for how their output device handles colour conversions.

Then again I haven't seen your file - and I haven't seen the output - or the file they output - so going on the evidence so far - the onus is on them.

[nawest]

Thanks Eugene, I'm of the same opinion that the issue lies with the RIP. Research suggests there's a few reasons why the RIP would make such changes especially on large areas of grey, but I'm not in control of the RIP and have little influence. The printer did look into the issue and, as a test, asked me to convert the Indesign file into Illustrator (their weapon of choice) and resupply. They then exported a PDF from the ai file at their end and the resulting print came out fine (which it would). They have asked that all future PDFs be exported from Illustrator! For so many reasons, this clearly isn't the solution.

It's been a fair few years since I worked in repro, but I recall we had the ability to visually check the RIP'd files onscreen before printing films (yes, that long ago!). This particular printer doesn't appear to have that facility, so the RIP'd files go straight to print without checking, and it's only at that stage that any issues become apparent. This appears to be a glaring omission to me, and the inclusion of such a facility would make at least the testing so much easier.

I've passed my research onto them and am awaiting a reply.

[Eugene Tyson]

There you go - my inkling was right - at least I think it is - I think they are opening it in illustrator which is wrong.

Any printing house asking to you to submit everything as Illustrator or Illustrator PDFs are not worth their salt. 

I'd be inclined to ditch them to be honest. 

This is my personal opinion.

[nawest]

No, not quite. They weren't opening the indd PDFs in Illustrator, they asked me to convert the indd to ai at my end and supply it so they could create a PDF at their end. Their resulting PDF did indeed print pure black. They have now used this as a justification to say that ALL PDFs should be exported from Illustrator as InDesign is clearly the problem. A conclusion I don't agree with.

I did supply them 'identical' PDFs from both InDesign and Illustrator of the same piece of artwork for them to try, but as yet, they haven't.

I also don't have the option to dump them, I'm sending the artwork where the client directs me to do so and, TBH, this is for the first major issue we've had with them in many years. I'd rather get to the bottom of the problem, solve it and move on where we left off.

[Eugene Tyson]

How do you know they didn't?

My suspicion is they are. You have no idea what they are doing. Whatever they did is making a mess of them

I've seen it before. Printers opening pdfs in illustrator.

I'm not saying it definitely happened but for them to suggest illustrator is a clear red flag for me.

[rob day · Accepted solution]

sent to various large format printers

Hi @nawest , With very few exceptions large format composite inkjet printers handle final color conversions internally—the profile for an inkjet printer is very different than an offset press profile.

You are preparing your files as if they are going to an offset press running to the CMYK FOGRA39 press profile, and exporting to the PDF/X-4 press preset, which does not include profiles for document CMYK colors. PDF/X standards include an Output Intent profile, which your RIP would not likely see. So your inkjet printer doesn’t know how to color manage the CMYK colors with no source profile.

You could try including all profiles—something like this:

[nawest]

Thanks Rob

I suppose you could call it ignorance, but even after many years in the industry providing artwork to many clients and printers, the area of colour management is still somewhat of a grey area for me. That said, the number of times that issues have been raised in those years would imply that 99.9% of the time it hasn't been an issue.

That said, you're right, I'm supplying artwork spec'd for offset printing and not large format digital, but in my experience very few printers, litho, flexo or otherwise, supply specifications for this level of detail. They'll invariably just ask for hi-res PDFs with fonts embedded, and no mentions of standards or profiles. It's only on occasions like this whe jobs go wrong that the question gets asked.

I'll certainly send them a new test using your suggested settings though.

[rob day]

that 99.9% of the time it hasn't been an issue.

Is your output typically to composite inkjet printers or offset presses? The color mangement for inkjet is really different.

[nawest]

I would say 80% inkjet, 20% offset (but a lot of this could actually be digital as opposed to traditional litho)

[rob day]

I would say 80% inkjet

Ink jet printers typically have a larger color gamut that offset CMYK and use RGB output profiles. If you send CMYK color, there would usually be an additional color conversion at output, and you might not take full advantage of the larger inkjet color gamut. You can use Proof Setup and Proof Colors to proof to an RGB output profile.

Here’s an RGB Output Profile for a Canon Pro inkjet printer in Apple’s Color Sync Utility:

[nawest]

Are you saying that the InDesign file would ideally be set up as RGB instead of CMYK?

The printer has now requested PDFs to be exported as PDF 1.4 with no standard, and with the profile inclusion policy to 'include tagged source profiles'.

What difference should this make?

[rob day]

PDF 1.4 with no standard, and with the profile inclusion policy to 'include tagged source profiles'.

I would set Profile Inclusion Policy to Include All Profiles. If you use Include Tagged Source Profiles, only placed objects with embedded profiles will export with source profiles. InDesign color would export as Device RGB (no profile)

When the printer is handling the final conversion to the print profile at print time, you want all color to be profiled. Here I used Include Tagged Source Profiles and this green fill exports with no profile:

[rob day]

Alsoas mentioned earlier, you can use Proof Setup / Proof Colors to preview in the color gamut of a composite RGB printer. Here I’m soft proofing output of an out-of-gamut color to the Canon PRO-1000 printing on fine art paper. Proof Colors shows the expected shift when the color is printed:

[Mike Witherell]

Since it is a large-format inkjet printer, you should build RGB in InDesign, placing RGB images into InDesign, and export to an RGB PDF. It should be possible to download the same printer driver they use for production and tune all your color management to that printer driver icc profile.

[nawest]

I'm confused. I produce artwork for both offset and large format and have ALWAYS used a CMYK setup. Why, when both print processes use CMYK inks, would I create or export in RGB for large format? I've never known a printer request RGB PDFs - it's always CMYK. And that's before I start thinking about actually working in RGB and CMYK. How do I convert a 68% black tint in CMYK into RGB?! So many questions. My mind is boggled!

I can see that after all these years of producing artwork for print that I'm going to have to do some more learning!

[rob day]

How do I convert a 68% black tint in CMYK into RGB?

Unlike Photoshop and Illustrator, InDesign does not have a single document color space. You can use RGB, CMYK, or Lab defined colors and objects on the same page and decide to color manage a convertion from CMYK to RGB in the document, or on an Export to PDF.

Here my document’s RGB Assigned Profile is Adobe RGB, and the CMYK assignment is Coated GRACol. If I convert this 0|0|0|60 CMYK fill to RGB in the document or on Export, there is a color managed conversion from Coated GRACol to Adobe RGB. The color appearance in this case doesn’t change because the gray color is in both the source and destination gamuts:

If the destination is a composite RGB printer, I could also make the same conversion on a PDF export and include the RGB profile like this:

[Mike Witherell]

Although large-format printers will operate 4-8 ink cartridges (starting with CMYK, at least), their computer brain RIP is designed to receive and process RGB color information. It decides how to translate it to its physical cartridges of ink.

So, if you feed it CMYK numbers, it likely will convert it to RGB numbers, and then RIP it to operate the CMYK cartridges. That is introducing a double-conversion that is effectively limiting the fullness of the color that could be.

[nawest]

I've used RIPs but am nowhere near an expert on their internal workings, but I find it bizarre if what you say is correct that they convert CMYK into RGB and then back again into CMYK. Why would they do that instead of essentially doing a pass-through? Surely the planned CMYK or Pantone colour mixes could/would change in the process.

[rob day]

Hi @nawest , Just to clarify, when you send the job to a composite large format inkjet printer it is the final output, and you are not proofing for an offset press? You don’t want to purposfully clip the inkjet printer’s larger color gamut right?

[Brad @ Roaring Mouse]

This IS correct. Because an inkjet's gamut is much wider than typical CMYK offset printing, even if the inkjet only has CMYK inks, ICC profile Management will change the the incoming data, be it CMYK or RGB to the color gamut of the printer, and it does this by converting it back to RGB (or LAB) so if you ae sending 100K to it, it will then find the closest match to what that printer can print to "match" what 100K would like printed on a sheet of paper. In reality, 100K on a printed sheet will not be solid Black anyway; the paper soaks a bit of ink up, so at nest you will get a dark grey. Proper color management will match that dark grey on your inkjet.

If you are getting incorrect (shifted) colors, the wrong Profile is being used for the paper being used, OR the machine is out of calibration.

I have a 12-ink HP z3100 and it needs to be calibrated every so often to keep it in line. Fortunately, my machine has a built in calibrator/spectophotometer so the process is pretty easy. Plus it will create its own profiles for any paper I put in it.

[Brad @ Roaring Mouse]

It also depends on the RIP. My HP has a Postscript RIP, so the data is sent to it in CMYK (if it exists) and RGB (if it  exists), and then the data is color-managed it. A non-PS printer does NOT stream CMYK data, they are RGB based, so your data is converted to RGB (usually at the driver stage) and then the printer color-manages that information. 

[reproo2773183]

Original question is why are they printing my tint of black with cmy?

Suggesting to work and export in RGB will give you expanded gamut on inkjet but it will also definitely convert Blacks and greys to print using all inks.

Looks to me either their settings in the RIP to keep greysclae as greyscale is incorrect.

Or putting it through Illustrator is the cause, could be Illy's CM Prefs and Policies, could be Exporting to PDF or Print.

My experience with Ink-jet proofs is that for four colour work the RIP can convert to RGB and regenerate the black channel and its difficult to stop this behaviour, to do it properly it has to build a DeviceLink profile to go from one cmyk profile to another cmyk profile and not change the black generation significantly. Most RIPs will have a button saying something like Pure Black ON and/or Print Grey Using Pure Black Only, or if its a completely Mono job you can force the whole thing to Greyscale in the RIP.

If you don't need the expanded gamut, I'd disagree with the advice to work in RGB and stick to cmyk and greyscale.

If you use RGB you are always going to get multicolour print.

If you add profiles to cmyk, then you are relying on the RIP to know what to do with them.

I'm comfortable with stripping the cmyk profiles and replacing them internally, knowing that the next stage of my RIP will convert to suit the paper stock. CMYK profile to CMYK profile conversion usually does more harm than good, specifically to do with the black generation, that's why Adobe has the CMYKsafe Color Management settings in InDesign.

On top of all that PDFX4 will have an Output Intent profile that simply isn't seen by either InDesign or Illustrator .

[nawest]

Thanks for that, your experience of working and outputting in CMYK is certainly more in line with mine.

I know all RIPs are not the same but for yours, what PDF standard, compatibility and profile inclusion compatibility would you use/recommend?

[reproo2773183]

I work at a small printer, we have a B2 litho press, A Canon toner based Digital Printer, and an Epson Inkjet, mainly used for Fogra 51 proofs which we'll try to match to.

In a nutshell I do not want DeviceRGB in your PDF.  So there are two settings that work:

PDF standard: I don't mind, I'd prefer that this doesn't flatten the transparency.

PDF compatibilty: v1.6* or above for anything RGB, if you're Converting to CMYK then v1.4 or above is fine.

Profile inclusion: Either

Convert to Destination: Fogra39 or 51, PSO Coated v3 ISO Coated v2, then Profiles are either Not included or Include ALL profiles.

OR

for RGB

No Color Conversion and Include All Profiles

OR extremely rarely for InkJet expanded gamut 

Convert to Destination, AdobeRGB(1998), Include All Profiles (I'm not averse to eciRGBv2 and also planning to try Rec2020 in the future)

* My RIP has an unresolved problem with profiles that start as V4 and are "modified" by Indesign to V2 in the PDF.

If the compatibility is v1.4 or below this happens. I can't preflight this problem because the "name" of the profile is not how the search for an icc profile identifies the profile.