Color space confusion (cyan color tint)

[Cobalt]

In Affinity starting with an RGB value of (100,100,100) translates to a CMYK value of (60,52,52,21).
-> Why so much cyan ?
-> Why is it different than this ? (here or here)
-> If I plug the CMYK (60,52,52,21) in reverse here I get rgb(80,95,95) with a cyan tint, but affinity says rgb (102,100,100). Why ?

In the attached file the color format is set to CMYK with profile (US Web coated SWOP v2).
-> Exporting the file to PNG gives me correct result (exactly as shown on screen) 
-> Exporting to JPEG with color profile included gives me a cyan tint. Why ? (it doesn't include the profile after all ?)

ColorTest.afdesign

[lacerto]

(...)

[mac_heibu]

Explaining and understanding color management definitively isn’t an „in depth subject" for a user forum. In Germany color management is an integral part of the apprenticeship of a number of press, prepress and design professions – each one with an educational duration of 3 years.

You are basically asking, why there are such big differences, when converting RGB to CMYK and vice versa. Short answer: It has to be so, and there is no way out. Why? Additionally to Lagarto’s explanation, you may read my answer (Juli 21) here:

 

 

[Cobalt]

@Lagarto

-> ok, the jpeg is in CMYK format. Still, why does it look cyan ?

->So, when I sent this file to the printer (as a PDF with the ICC embedded) and their print is cyan tinted (like the jpeg above) whose fault is it ?

[Cobalt]

@mac_heibu

Indeed color management is a complex topic.

Recently I sent a PDF file to a printer (the Affinity document was in CMYK and I embedded the ICC profile during export).
95% of the file was neutral gray with a few touches of color in a couple of places.

All grays came back cyan tinted. The printer argues with me that all my Cyan values are elevated like the OP example CMYK (60,52,52,21) and they claim it is my fault.

I don't understand why say that. I thought once they have the ICC they can work back to neutral.

[lacerto]

(...)

[lacerto]

(...)

[Cobalt]

@Lagarto Thank you for explanation. It open as you say in photoshop indeed. It looks like some image editors ignore the color profile (like the attached image of the OP). XnView even reduces it to 8bit before opening it.

[Cobalt]

5 minutes ago, Lagarto said:

Colors are complex. How badly were they tinted -- ever so slight cyan tone can be expected with these values, but it also depends on paper, and naturally on viewing conditions. If you want to have absolutely neutral grays, you should use mere K values. 

@Lagarto Compared to the gray card (bottom of attached photo) there is a significant tint I think. Is this normal ? (unless we are looking at ghosting and their cyan plate is not properly aligned ?)

[lacerto]

(...)

[Cobalt]

5 minutes ago, Lagarto said:

Certainly not. Did you get this with the mentioned CMYK values?

Yup !

[lacerto]

(...)

[Cobalt]

3 minutes ago, Lagarto said:

If you stil have the print pdf of the book cover and open it in Photoshop, do you get the same values? If you do, I'd say the printer has made a mistake. One possible explanation may be that the deep black in the cover may have contained too much tint for their process and they have run a routine that reduces tint. In that process, the grays have changed, as well, but in a way that has caused cyan to become too prominent.  

Yes, the PDF opened back in Photo displays neutral as expected and the CMYK values are mentioned earlier.

Thanks for your thoughts on this. At least I am not going crazy.

[R C-R]

5 hours ago, mac_heibu said:

You are basically asking, why there are such big differences, when converting RGB to CMYK and vice versa. Short answer: It has to be so, and there is no way out.

Maybe a bit off topic but I recently discovered a free online book called Programming Design Systems by Rune Madsen. Several of the chapters in the Color section, particularly the comparison of additive & subtractive color mixing in the A short history of color theory chapter & the discussion of color models, color spaces, & color profiles in the Color models and color spaces chapter, shed a bit more light (pun intended) on why this is (& has always been) true.

The Perceptually uniform color spaces chapter is also interesting (if you are into that sort of thing), particularly the mention of the HSLuv color space & the link to the interactive HSLuv color chooser. I don't know of any app that includes that chooser or how useful it would be if any did, but if nothing else playing with it gave me a better understanding of the shortcomings of the traditional HSL picker.