Color mixing in CMYK

In one version of Krita (I don’t remember which one) they had the option to mix CMYK colors. But there was something strange. In true CMYK colors are measured in percentages from 0 to 100%… and in that version, the scales were “RGB style”, going from 0 to 255! The black obtained, for example, looked like a very dark gray.

I thought this would be fixed in later versions, but it never came back…

It’s sad because I still haven’t gotten around to mixing RGB colors, I’m used to mixing CMYK colors, I find it much more intuitive. To get shades of yellow in RGB, for example, I have to resort to a palette I used in Gimp… and it’s hard for me to get the right shade.

Are there plans to implement CMYK in Krita? I say for mixing colors, as it is in Gimp (although in Gimp 100% Cyan is too light, I can get around it by mixing a little Magenta…)

Nobody? :frowning:

CMYK is already implemented in Krita. It’s just not used for painting, but rather printing.

GIMP doesn’t use CMYK.

Maybe you are talking about mixing RGB colours as pigments? Here is another discussion with a lot of info. I think you can do it with krita.

Here we have a strange situation:

• GIMP lets you compose and mix CMYK tones, but it does not work with files configured for CMYK. I know because I tried to open a Photoshop psd file (which didn’t contain any layer styles or anything special) and GIMP warned that it didn’t work with CMYK files;

• If CMYK is implemented in Krita, then why can’t I mix CMYK colors? How am I going to set up a print color if I can’t even see it?

Just to be clear, RGB is a suitable system for everything that involves video. For printing the RGB system does not work. In the RGB system, for example, you lighten/darken a color by increasing/subtracting light. In printing, in the current state of technology, this is impossible: to lighten/darken a color you get by adding or not adding ink.

Another example: in the RGB system, the mixture of Red, Green and Blue colors form Black. In print, if you mix these three colors you won’t get a pure black: it will be more of a very dark gray…

Have you tried using soft proofing to check your colors? I don’t really print my work but i always hear that trying to work directly with CMYK when you are going to print is a mistake. The more correct way would be using RGB even when you plan on printing later.

CMYK will also lock you out of many blending modes cause they can’t work with it. One thing you could try is changing your color wheel color space to CMYK but keep the document in RGB. According to a friend he was able to get a good accuracy working like that. You can also activate gamut warnings to make sure you are working inside it.

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Krita’s Specific Color Selector allows you to select in CMYK even when you work in RGB, and you can set it to percentages aswell.
And if you work on a CMYK document, the foreground color dialog will also show a CMYK based selector, with Cyan+Magenta in one square and Black+Yellow in another (the channel combinations can’t be changed currently…)

Regarding Gimp, you probably didn’t set a CMYK profile, then it doesn’t use “real” CMYK mixing, but a pseudo-CMYK that is just an inverted RGB model, thus giving you the full RGB gamut.
If you go to the preferences and import Krita’s “Chemical proof” CMYK profile, then, surprise, you get the same colors in Gimp as in Krita.

That “fake” CMYK (no profile in Gimp) does not reflect how “real” CMYK works at all. In reality, there is no pitch black ink or paint (not counting some nano-tech coatings like Vantablack that come very close), and all inkjet printers I’ve used so far did mix other colors with black ink to print the darkest black, unless you set it explicitly to grayscale mode to save color.

The printing cyan is also quite different from RGB “cyan” (max blue+green), you can’t get the latter at the same relative brightness and saturation as on your monitor, it’s either darker or less saturated.

You can select cmyk colors in the colour selector and also you can use percentages in the specific colour selector docker. just press the percentage button and select cmyk colour profile from the drop down.
Screenshot_20220511_193131

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To add to this information, you can also do the same with the advanced color selector.

• LunarKreatures: My last job was as a designer in a fabric print shop. One day my boss received an RGB file and tried to convert it to CMYK. He did not make it. Of course, there are files that can be converted, without any problems, from RGB to CMYK… but the ideal, if you are going to print in CMYK, is to create - and work with - the file in CMYK. Enabling Gamut Warning only partially solves the problem.

• Lynx3d: True, Gimp’s CMYK is fake: his 100% cyan is too light, as I said. Still, it’s easier and more intuitive to mix colors by a CMYK picker. If I give three pots of colors each in red, green and blue to a person and ask them to give me a shade of yellow… they will find it extremely difficult. This is the point!

• raghukamath: Thank you! It was what I was looking for. The only problem is that I’m used to mixing colors from the top menu via the “Select a color” dialog box… this is because I like to change the palettes sometimes. The palette I use is too basic…

• LunarKreatures: I couldn’t change the advanced color selector.

Here’s a screenshot, taken just now:

It’s possible the file was not made with the limitations of CMYK in mind.

I strongly disagree with it but it’s your choice to work like that.

In the advanced color selector settings you need to check uses color space different from image and set up the one you want

That may be correct if you use a software that does NOT offer soft-proofing, but otherwise it hinders you to profit from that software’s full potential, its possibilities.

Michelist

You can open the palette docker separately too and selecting a colour in specific colour selector will also make it your foreground colour then you can add this colour to the palette just by clicking on empty cell in the palette docker.

Another work around, which might be cumbersome to you, but if you have to use the colour selector from the top bar no matter what, then there is a way. Most input boxes in Krita support math operations. so you can input something like 255/2 or 255*0.5 to get 50% of any colour, or say 255*0.35 to get 35% etc.

You can just use Pigment.O plugin and work on a CMYK document and it will work in CMYK automatically with CMYK display too. But using 255 on it will be better than 100 because of conversions but if you really want you change also but I won’t recommend it. Regardless as you move the sliders percentage values will be displayed independent of the range you have or set.

Also Pigment.O has an independent colour mixer in CMYK, but it is not a canvas mixer you have to set the colours to mix and then select the mix amount. This can give you any mix in any colour space.

I worked at a print shop and I never had issues with files not being able to convert to CMYK. Also when you do soft proofing you gotta alter things manually so it becomes clean in CMYK. soft proofing is just a indicator not a conversion.

Why are you using a RGB document if you want CMYK that much ? What do you mean by fake CMYK in GIMP?

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• LunarKreatures: I don’t know the source of my boss’s file, it was provided by a client. As for working with CMYK, it’s not my choice, it’s the job market’s choice. An example: one day I showed my work, the person asked if I had done it in Photoshop. I said no, it had been done in Gimp. The person had never heard of the Gimp… :frowning:

• Michelist: I think they implemented this much later in the company. For my part it made little difference as I was working in Photoshop, using CMYK. And, as I said, not by choice of mine: the company already used this system of work.

• raghukamath: In my case, the problem is more the habit. For example, if I want a yellow one I go straight to my basic palette (which I had originally created for Gimp). Then if I want lighter or darker, I move directly in the triangle.

An interesting feature of this calculation. Unfortunately, I’m not very good with math operations…

• EyeOdin: I’m using RGB for now, just for personal work. What worries me is this possibility: I create wonderful art in Krita, an eventual client would love it… but there was a problem when converting to CMYK.

Yes, I know, a lot of people will say: “It’s okay to work in RGB, I send it to the printer and they print OK”. But the printer only prints “OK” because they were successful in converting to CMYK! Even so, there will always be differences between color systems. That’s why it’s more guaranteed to work in CMYK.

As for the “GIMP cyan being fake”: 100% cyan comes out lighter. The screenshot below has a comparison. The website is Color Hexa:

that is happening because Gimp does not have a acctual CMYK document to display on screen. Converted that is the math. strangely enough I think the math might be right it is Cyan. On a cmyk document this is the result with Krita.

GIMP don’t open CMYK files… at least, not the Photoshop file I tried to open. To this day, I don’t know why: in that file there were only normal style layers with solid colors and drawings. I’ve already managed to open files with layer style in Krita and the result was satisfactory…

Well, math is not my strong point. The 100% Cyan I remember is more like that site.

There is no Cyan 255: this is RGB scale, not CMYK. CMYK is measured in percentages, from 0 to 100%.

you should be opening it on Photoshop if it is a PSD file, not Gimp nor Krita. You have to actually “Export” if you want that.

Yes “Percentages”! 100% of 255points max is still 100%. 100% of 3000points max is still 100%. I get you perfer the 100 range limit but a percentage is still a percentage. Percentages are relative.

@Guerreiro64 bear in mind that as long as you are viewing your work on your computer you are seeing it interpreted by an RGB device. What you see in your screen won’t match the CMYK you think you’ve used. You need to print your work to see if your CMYK assessments are what you really have.

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• ArtViking: This depends on monitor calibration. Where I worked this was done and the result on the screen came very close to the print. The only problem with the calibration was that you couldn’t possibly tamper with the monitor’s brightness/contrast controls… and some idiot at the company almost did that to my monitor! :smiley:

Yes, I am aware of the differences. I noticed this when working with old versions of CorelDRAW. There was, in the program’s color palette, a very nice shade of brown on the screen. A client even chose that tone for the art of a sticker.

But in the CMYK composition of the color it had more than 60% black. The print came out a dirty gray. As he had sent the artwork ready, it wasn’t my fault. I don’t know if the problem was with Corel, the monitor without calibration or both.