Why is the embedding of RGB profiles so important?

A few days ago we received a call from a customer in the field of design, who sent open Adobe InDesign data in ISOCoatedV2 300% with contained RGB images to the production company for a complex CD production on the advice of the producing company (“The printing company still has a prepress stage, which can then prepare your data optimally…”). The result of the finished printed CD booklets and inlays did not correspond at all to the calibrated monitor image of our customer, the client was also unhappy and requested the print data about the production company from the print shop responsible for the print to troubleshoot. Data in the “US Web Coated” color space with 350% ink coverage came back from the printer. For troubleshooting, the customer then had a proof of his data created by us, but had chosen the settings “Convert to target profile (retain values)” as usual when writing the proof PDF; we thus received completely CMYK data, of which we produced a proof according to ISOCoatedV2 300%, which completely met our customer’s expectations. So it seems that the designer created the data correctly and printed the print shop incorrectly.

On closer inspection, our error analysis revealed two serious weaknesses:

  • On the one hand, the obviously wrong profile conversion of the print shop with InDesign CS2 to “US Web Coated”, a completely outdated profile never used in Europe, which was delivered with early Creative Suite versions and was probably never adapted due to a lack of competence on the part of the print shop.
  • On the other hand, the open InDesign file of our customer, which he had sent to the production company, contained RGB images without a profile (DeviceRGB), which cannot be safely interpreted.

In this case, a complaint of the designer to the printing company will of course be difficult, as on the one hand, non-profiled RGB data were sent to the production company, and on the other hand, no print PDF generated by the data creator in the correct output color space ISOCoatedV2 300% was supplied.

If this had been done, one could at least have argued that the expected color of the production print would have been comprehensively known. Thus, one can only refer to the fact that the printer would have had to ask the designer for RGB data without an embedded color profile, and should not have assigned the data somehow to a profile “blindly”. The fact that the print shop with its crude US Web Coated workflow certainly did not create a correct print file, but a wrong one for the output, can indeed be stated, but the print shop can always talk its way out to “systems with in-house standard”.

How do we deal with RGB data at Proof.de?

If we receive a PDF file that contains RGB images, the next step is to check if the file is a valid PDF/X-3 or PDF/X-4. If this is the case, we check whether all input RGB profiles are correctly marked with color space (sRGB / AdobeRGB / ECI-RGB-V2 etc.) and rendering intent, then we check whether the correct output color space was used as output intent and whether also contained CMYK data have the correct input profiles. If yes, then we proof the file with the settings: “Consider all input and output color spaces”.

In this case, the file is reproduced 100% exactly as our customer created and defined the color profiles. If he has made a mistake and e.g. marked an image with a wrong RGB profile, this will also be “incorrectly proofed” exactly as correctly.

If RGB data should not contain a profile, e.g. if they are created in Device RGB, we generate a “data incorrect” e-mail in which we explain our procedure as follows:

“Dear customer, the data check has shown that RGB elements are contained in your data. RGB elements can only be safely interpreted in the proof if they are marked with a color profile and a rendering intent. This is the case, for example, with correct PDF/X-3 and PDF/X-4 data. The correct output intent must also be specified.

At least one of these criteria does not seem to be the case for your file. The safest way would be to convert the contained RGB data to CMYK. This has the advantage that you have control over the conversion and can view the CMYK result again in Acrobat before uploading the file again for proofing. We can then reliably use your CMYK values for the proof. To do this, call up the current order in your customer account, delete the incorrect data and upload the corrected data.

If, for example, the RGB element should only be a small image that is not relevant for the overall impression of the proof, or if you do not have another file available for the proof, then of course we can also use your RGB data for the proof. If available, we use your RGB source profiles and rendering intents, otherwise we use the sRGB standard and the rendering intent “relatively colorimetric with depth compensation”, which in most cases will lead to correct proof results. If you would like us to proof the supplied RGB data in this way, please let us know. Please do not hesitate to contact us if you have any questions. Best regards, your proofing team”.

In our case, the CD production case would also not have occurred in the proof, as we reject RGB data not provided with an ICC profile with the error message mentioned above, and do not convert them, as we cannot predict precisely how our customer would have liked the data to be converted.

We are aware that our approach is not 100% the ultimate best approach in all cases, but to the best of our knowledge and belief it is best in line with market practice and the expectations of our customers.

However, we are also happy to accept your individual requirements and circumstances. Give us a call or send us an email and describe your processing requirements.

Colour Management Consulting and Expertise

Colourmanagement Consulting

Colourmanagement Consulting

By the way: We are happy to put our knowledge and data competence at your service: If you also have a problem, a question about print data, data preparation, or – as in the above example – a misprint has already occurred and you need external expertise and assistance for the complaint: Give us a call. We will be happy to advise you and help you where we can help. We will charge you for our advice and analysis at an hourly rate of EUR 90,- plus VAT, and you will be billed for 15 minutes each. An initial consultation and assessment is of course free of charge.

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How CMYK and RGB profiles are handled in proofing

When we receive a file from you, the first thing we check is whether there are colors other than CMYK in the file. If the file is built exclusively in CMYK, it will be sent directly for proofing.

Handling wrong profiles with CMYK data / “Profile Mismatch
If we have only received CMYK data from you, we will ignore all input and output profiles and only use the CMYK values that we bring to the ordered output color space.

Example 1: Data in ISOCoated, proof in ISOCoatedV2 ordered, thus wrong or no CMYK profile embedded.

You send a file with the profile ISOCoated and a color area in CMYK 100/70/0/0 and order a proof according to ISOCoatedV2.
We ignore the ISOCoated profile and proof the pure color value 100/70/0/0 according to ISOCoatedV2.

Why do we do this?
In our proofs, we try to reproduce the “lived reality” of the print as well as possible. In many conversations with printers we have seen that in almost 100% of the cases they do not convert profiles from CMYK to CMYK, but instead put a colour value of 100/70/0/0 on the plate without taking CMYK profiles into account, insert paper and print in conformity with the standards. So we also map this way, although it would actually be “more correct” to perform a color space transfer from ISOCoated 100/70/0/0 to ISOCoatedV2. However, this results in a different color value, for example 100/63/1/6 for relatively colorimetric conversion with depth compensation or 100/63/3/15 perceptively with depth compensation!

In practice:

One of our customers did not proof 30 slightly different, dark blue colour areas in ISOCoatedV2 on our premises, but on the premises of a colleague, under each of which the CMYK value was in black lettering, in order to sample the colour of a powder-coated surface. The customer defined a very well fitting CMYK colour value on the basis of the proofed colour areas, inserted it into his brochures and started the print jobs. Result: The dark blue was a distinctly different blue than on the reference proof, customer and agency were very dissatisfied and went on troubleshooting. Now the case came to us.
We received a file for proofing according to ISOCoatedV2 and compared it with our colleague’s proof. The colors with the same black CMYK values printed underneath were clearly different, but both proofs were provided with media wedges and measured correctly. After some troubleshooting, we came up with the idea of requesting the original proof from our colleague, which also existed. In this one there was a Fogra27Coated profile, thus an implementation of the old ISOCoated. A proof according to ISOCoatedV2 had been ordered at that time. Had it happened? The colleague had taken the input profiles into account, which resulted in a significant change in the CMYK values of the color patches, as mentioned above, due to a color space transfer from CMYK to CMYK. The black printed CMYK values under the color patches had of course not changed. The patterned CMYK value therefore did not correspond to the proofed value at all. Our customer fell from all clouds: “How, our CMYK values were not proofed”. This would not have happened with us, because we would ignore the embedded profile with CMYK data. In this case this would also have been our customer’s expectations.
After almost two hours, we had determined the “error” (or perhaps rather: the “difference”), created a proof for our customer that was “in line with expectations”, which he could use to determine the appropriate CMYK value in ISOCoatedV2, and solved the problem. Continue reading

Easy conversion of Pantone – HKS – CMYK – RGB with Adobe Photoshop

Farbbücher Auswahl in Adobe Photoshop CC: HKS, Pantone, CMYK und vieles mehr

More often the question arises as to what kind of Pantone colour corresponds to the HKS 43 K. Or what CMYK value? And what kind of web color in RGB?

If you own Adobe Photoshop, you can do these conversions directly there. In Photoshop CC all well-known color books are stored with values.

Let’s assume we are looking for the Pantone equivalent and the matching CMYK color of HKS 43 K.

1: Open the color palette in Adobe Photoshop and select HKS K as the book and then the color HKS 43 K. All well-known colour books are directly stored in Photoshop.

Farbauswahl von HKS 43 K im Buch HKS K in Adobe Photoshop CCThe color corresponds to a Lab value of 26/29/-79 and a CMYK value is already stored here. Simply select the book HKS K Process: Continue reading

Layout in RGB, print in CMYK. Problems?

Especially in larger companies today the layout in RGB is the rule rather than the exception. The advantages are obvious:

  • The layout takes place in a large, almost media-neutral color space
  • All Photoshop filters are available without restrictions
  • The process of color space conversion to CMYK is shifted to the production process as late as possible

In practice, however, there are two potential problems in particular.

Problem 1: CMYK conversion in the last step.
The catalogue is designed in InDesign, all data is perfectly matched, the last step before printing and proofing is the export to a printable PDF in CMYK. Usually this is done via a preset in InDesign, which defines the exact specifications for the color space conversion. In practice, however, this color space transfer can hardly be monitored. The problem: Even if you check the color values in Acrobat in the exported PDF file, for example, Acrobat does not really display the colors it contains. Acrobat brav would show you CMYK values even if the RGB images are still wrongly contained. However, other CMYK values can occur during printing when the data is processed again. Lately it looked like this:
Continue reading

Why monitor and paper don’t get along when it comes to color.

Colour is colour, you’d think. That’s right. But have you ever tried to explain the colour of your new car or your new red wallet to a friend on the phone? You will notice that human color recognition and the reproduction of the same in another medium is very difficult.

The same applies to computers – better: monitors, and printers – i.e.: laser printers, inkjet printers or newspaper printing or offset brochure printing.

Why is the red on a monitor different from exactly the same red printed on paper? It’s simple: put the paper in front of the monitor. The two shades of red are exactly the same. Like this. And now you’re completely darkening the room. What do you see? The red on the monitor is still red. And exactly the same red on paper? This is black now. Why is that? Very simple:

Translated with www.DeepL.com/Translator

A monitor adds light, i.e. spectral components, to the existing ambient light. If you see red on a monitor, it is because the monitor actively emits red light.

And now the paper: When do you see red on paper? Exactly when white light falls on the paper, for example through a window or a lamp. And when do you see the color red on paper?

When white light falls on the paper and the paper extracts the non-red spectral components from the white light and reflects the red light. That’s when you see the color red.

One colour, two completely different ways of production. And this is exactly where the color calibration and the proof start. The strategy? Fairs. And this under fixed conditions and not with the human eye, but with “incorruptible” technology.

Put simply, a monitor calibration device can measure your monitor and see exactly “how much” color your monitor can display, and “how wrong” your monitor can display color. And if your computer knows that, it can correct the monitor.

Another measuring device can emit neutral white light onto a paper and measure the reflected color. Depending on the printing process and paper, the ink looks completely different, but the meter again sees “how much” ink the print can represent and “how wrong” the print represents ink. And if your computer knows this, it can correct it. And:

If the computer knows the color representation of the monitor and printer, it can correct and adjust the representation so that both correspond to the same color. Of course, this only works if the color and brightness of the light that illuminates the paper is also known and standardized.

And how does the proof work? Very simple:
If a computer also knows that the final printed product is to be printed in offset on an image printing paper, and it knows the colour representation of this printing process, then it can simulate this on a monitor and on an inkjet printer.

On the monitor, this color-accurate representation is a so-called “soft proof”, the color-accurate preview of the subsequent print on the inkjet printer is called “Proof” or “Contract Proof”.

This inkjet printing must be very precise and meet the highest demands in gamut and color simulation. And since the image processing technology, color matching calculation and measuring technology behind it is not very cheap, proofs are still mostly “expensive” inkjet prints. Due to new printing systems and inexpensive and better measuring technology, however, prices have also fallen significantly here in recent years.

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What’s a proof for? The most important reasons for proofing!

  1. A proof is reassuring:
    The proof shows the colour result of the subsequent printing.
    The customer knows exactly the later result from the proof and is reassured.
    The printer knows that the customer knows the proof and is also reassured.
  2. A proof is fast:
    Ordered today, delivered tomorrow: Modern proofing service providers work quickly and produce hardly any loss of time in the design and printing process
  3. A proof is precise:
    All professional service providers nowadays work with proof printers that are recalibrated at short intervals. A media wedge with test report also provides clear metrological proof that the proof is correct and within the limits of the standard deviations.
  4. A proof is cheap:
    In the past, repro studios often charged almost 30 euros for an A4 proof. Nowadays, it only costs a fraction. Proofing costs are of little importance in the production process.
  5. A proof also shows the colors that the monitor does not show:
    In most agencies, hardware-calibrated proof monitors are in short supply. And TFTs or old tubes show colors, but unfortunately some. A proof also depicts colors that standard monitors cannot display, but which can be printed.
  6. A proof simulates newspaper as well as coated paper.
    If the same advertisement is to appear in the glossy brochure for the trade fair stand, in the trade fair news and in the special supplement in the local daily newspaper for the trade fair, then the three different colour results can be excellently simulated and presented in proofs in advance. And who knows: Perhaps the customer will then have the house brochure printed on picture printing instead of on uncoated paper due to the proof, or will choose a different motif for the newspaper ad. The proof shows it.
  7. A proof can do CMYK and more!
    Modern proofing systems can reproduce up to 98% of all Pantone colours and HKS colours in the proof.  This means that not only four-color, but also five, six and multicolor files can be proofed. Today, proofing is often done twice: once in CMYK plus corporate color in Pantone and once in CMYK and corporate color in CMYK. The client and agency can then decide whether the colour result is worth the extra charge for the fifth colour in the print.
  8. A proof is made of paper.
    Just like the product he’s simulating. A proof can be placed next to the print and compared under Normal. And to check it out, you can carry both to daylight, look at them in the candlelight and much more. A soft proof cannot do all this.

This is the first incomplete list. You know of other good reasons? We look forward to any comments and would be happy to add further points.

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Embed profiles for proofing? Yes or No?

The question often arises whether color profiles should be embedded in the PDF files for proofing.

To answer the question, you have to get some answers: The proof should simulate the subsequent offset printing. For offset printing, with few exceptions, the imagesetters have been configured so that a 70% black in the file is displayed as 70% black on the printing plate, no matter what profile was specified in the file. It didn’t matter whether it was coated paper or uncoated paper: 70% in the file corresponded to 70% on the plate, the choice of the paper printed on resulted in the colour representation.

The proof has also adapted to this: Most proofing service providers ignore embedded profiles, as long as the data is in CMYK and do the same as their print colleagues. Even with grayscale, the profiles are usually ignored and the grayscale is simply assigned to the CMYK black channel. Thus all CMYK and grayscale data are simply interpreted as if they had been created in the output color space. If “ISOCoated V2” is proofed, all images are treated as such, and if “PSOUncoated” is proofed, then the CMYK images are created in this color space.

This is excellent for the majority of files to be proofed. Only RGB colors contained in the data are problematic.
Since the RGB color space is considerably larger than most CMYK color spaces, it must be clear from which color space to convert to CMYK according to which criteria. Most proofing service providers specify a color space from which they convert by default if no RGB color space is defined. This can lead to difficulties: For example, many proof studios choose AdobeRGB as color space because it is large and optimized for offset printing; however, most images from digital cameras come from sRGB and these color spaces differ considerably. Therefore, it is important that the RGB color space and the rendering intend is embedded for a proof, otherwise the proofing software normally selects a color space for conversion to the CMYK color space to be proofed; and this color space is possibly not the one in which the data has be created.

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