1

I am working with a publisher (Oxford University Press) and they require images to be supplied as CMYK. That's ok - Colour accuracy isn't 100% important.

I prepare my figures using RGB, then convert them to CMYK when I'm done. I am using CorelDRAW X7. When I open the CMYK figures on my computer, the colour doesn't look as good as RGB (as expected), but close enough.

I upload the CMYK figures to the publisher's online system and then it displays them back to me. However, the colour looks simply wrong. Some of the blues and greens are too bright, and there is an overall greenish feeling to the figures.

An example.

Here is the original RGB figure.

enter image description here

Here is the CMYK figure, when opening the CMYK figure, copying and pasting into the website here.

enter image description here

As expected, some colours are off. The croc head is less bright, and the bright pens on the top row seem a bit dull. But that's fine.

Now, when I upload the CMYK file directly I get this:

enter image description here

I believe the problem is obvious. It just looks green. As if some algorithm is overcompensating for the dull green generated by the CMYK.

This behaviour is not consistent. If I open the CMYK with Corel, Windows image viewer or paint.net, it looks fine (like the 2nd image in the question). If I use XnView locally, it looks wrong like the 3rd image here (and as it appears on the publisher's website).

What is happening and how can I correct it?

Some explanation as to why this is important. Even though the figures are part of an article that will go to press, it will also be available as a PDF for download. I expect that >90% of the people who will read the article, will read it from the PDF (which is presented as RGB on screens) and not from the printed version. If the publisher is mirroring back to me a wrong representation of the colours (as is depicted on the last image), how can I be confident that it will be correct in the final version?

Improve this question
1
  • 1
    You probably need to speak to the print company. But note that some viewing software doesn't support previewing CMYK images properly - that includes most browsers, and probably xnview.
    – Billy Kerr
    Oct 28, 2019 at 13:17

1 Answer 1

Reset to default
2

Ok, wait and stop.

Two parts here, first the important one.

As almost 95% of these cases... You do not mention at all the color profile you are using or need.

Corel X7 does a decent job when converting color modes, but you need to have it configured right.

  1. Find out what type of paper you are going to use. Mainly coated or uncoated. I am guessing coated.

  2. Define the region of the world and the specific profile the press is using. I am guessing Europe here, but one common problem is that people recommend Fogra profiles that use a TAC of more than 300%... and then they decide they need a 300% top.

I'm sorry, my Corel is in Spanish, but here is a screen capture:

  1. Go to Tools > Color > Default preset?

enter image description here

And on the screen choose one based on the information of the publisher.

enter image description here

Second part

But the specific problem you are describing is that you are testing your file on a heck of different programs that manage the color profiles differently. Some simply ignore them.

The last image you posted is simply discarding all the CMYK previsualization and colors profile because some web browsers can NOT handle a CMYK file correctly, so do not worry. The same on XnView.

The first image is an RGB file before the conversion it is probably simply using the RGB profile or not using any at all, which on an RGB file is probably not a big deal.

The second is one screen capture of the program actually simulating the color conversion. That is what a pro program do, give you a representation of the colors simulating how they will change on print. If you did embed the color profiles that will be fine.

The press is not going to open the file on a viewer, or a web browser, they will work within a workflow of programs that consistently handle the embedded color profiles and CMYK values. This is why the first part is the important one. The ideal thing would be that your monitor has some minimum calibration.

Let me spam you with an ugly old webpage of mine. https://otake.com.mx/ColorCalibration/ The most important part is the gamma. The modern standard is 2.2.

Edited. Part 3

You need to prepare two different PDF files, but not the color issue. Adobe reader is one of those programs that make a good representation of a CMYK file inside it. So you could see the final CMYK PDF file prepared from Corel and use adobe viewer to see it.

But in reality, you need to prepare a separate PDF to be viewed online for the file size.

When exporting a PDF File for prepress, the file is normally quite big for two reasons.

  1. The Raster images need to be at high resolution, let's say the typical 300PPI
  2. They need to be CMYK and with minimal compression, this is using only ZIP compression. Even using High-quality JPG compression (which I only recommend in case you know what you are doing) a CMYK file does not compress well.

For a good PDF to be viewed online it is a good approach to prepare a reduced version of the PDF, with images on RGB mode, resampled down, let's say to 100PPI which makes them 9 times lighter and with some good JPG compression to make them, not perfect but easy to handle. This will produce a PDF file lets say 50 times lighter than the one made for print.

Part 4

how can I be confident that it will be correct in the final version?

By maintaining al the Color Management workflow all the way. I will expand it from the photoshoot itself but highlight the ones relevant to your part.

  1. A good illumination with lights with good color consistency (No cheap fluorescent lights or cheap led lights for example)

  2. Good exposition and white balance on the camera. Images saved with a defined color profile.

3. Consistent management of the files, no discarding of the embedded color profile.

4. If for some reason the images have not an embedded color profile, you need to decide at this point to embed one. For print, a commonly used is Adobe 1998, for web-only sRGB, for both, stay with the Adobe one.

5. If you need to edit them, use a calibrated monitor and a program that actually previews this (Corel Draw and Corel Photopaint are a good option with the settings as I showed you)

6. Work in RGB as long as you can with the color simulation turned on, leave the conversion just as the last step.

7. Send a correctly prepared file with the profiles embedded.

  1. Ask for feedback of the printer.

  2. Ask for a digital print well-calibrated. This is easier if you live nearby, but sometimes they can send a printed simulation overseas... Ask.

  3. But the real thing is standing in the print room when the print is actually happening, and grabbing the first fresh samples. This sounds silly on these modern days but for some crucial projects, this could be imperative the first time you work with a new provider.

With a well-calibrated workflow, you can stop at point 8 and be confident that things will go fine.

An alternative tho steps 3-7 is to leave the color handling by a studio.

Improve this answer
3
  • Thank you for your answer. I added a small edit to my question to clarify some things.
    – Gimelist
    Oct 28, 2019 at 2:28
  • I added part 3, in reality the clarification does not change at all the first two points, but hopefully will give you a clearer track.
    – Rafael
    Oct 28, 2019 at 3:03
  • I added some more tips.
    – Rafael
    Oct 28, 2019 at 3:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.