Color conversion varies with the same settings

[PeterB.]

Hello,

I noticed an inconsistency when converting color spaces. Admittedly, maybe a bit special, but when you stumble across it, it's difficult to understand.

A colleague accidentally created a Publisher document that was actually intended for printing with RGB as the color space. The images placed in it were linked RGB images. Not a problem in and of itself, I thought. Then we subsequently converted the document into CMYK.

And here, some images suddenly appeared more “saturated” in color than those that had already been converted to CMYK using the same settings.

What I've found so far is this: Even if the (conversion) settings in Affinity Photo and Affinity Publisher are identical (relative colorimetric, black point compensation, color-profiles, etc.), the results of the conversion are measurable and visually different.

If you place an RGB image in an RGB Publisher document and then convert that document to CMYK, the result for converted image in that document is completely different from if you previously converted the image to CMYK in Photo and then placed it in the converted Publisher document. But actually the result should be the same with the same settings, right?

I have attached the example files from the screenshot in case anyone wants to test it.

Thanks.

Testdokument.afpub Testimage.afphoto

[Hangman]

Hi @PeterB.,

I have to say I'm not seeing the same issue...

Initial Document Settings

• Your Publisher document starts out using an sRGB Profile
• Your RGB JPEG uses a Display P3 profile
• Your CMYK JPEG File uses a PSO Coated P3 Profile

Change the Publisher Document from RGB to CMYK Using the same PSO Coated P3 Profile

• Place the JPEG files converted in Photo to CMYK into the CMYK Publisher document

This is the result I see... Am I doing anything differently to you here...

[PeterB.]

Hello @Hangman,

Thanks for testing. Would it be possible for you to post me a screenshot of your General Affinity Publisher color settings?

[Hangman]

Hi @PeterB.,

4 minutes ago, PeterB. said:

Would it be possible for you to post me a screenshot of your General Affinity Publisher color settings?

Of course... These are my default settings for both Publisher and Photo...

These are the Publisher Colour Settings used when converting the document to CMYK...

These are the colour profiles used for your RGB and CMYK JPEG files...

RGB

CMYK

Let me know if I'm doing something differently to you in this process and if so I'll ee if I can replicate it...

[PeterB.]

Hello @Hangman,

Thank you for sharing! I have set PSO Coated v3 as the CMYK profile in my settings because that is the prepress standard for Europe – as far as I know.

If I change the default setting to US Web Coated and convert, the problem doesn't actually occur.

Even if I leave the default setting on PSO Coated v3, but first convert the publisher document to US Web Coated, the problem does not occur.

If you have time, please try to see if you can reproduce it if you change the CMYK profile to PSO Coated v3 in the basic settings.

To me, this looks very much like a bug related to the PSO Coated v3 profile.

If you need to download the profile: http://www.eci.org/doku.php?id=en:downloads#icc_profiles_from_eci

Thanks!!

[Hangman]

Hi @PeterB.,

Regardless of the default working profile in Publisher, I don't see any issues... Here I've switched Publisher's default CMYK working profile to PSO Coated P3 and I have the same outcome...

[PeterB.]

Hi @Hangman,

thank you for making such an effort. I think I expressed myself too misleadingly.

The top test image on the left is an RGB image. From what I understand, after converting the document, Publisher shows me the image as it would look if I had it already CMYK. Or am I thinking wrong?

This means that, conversely, the image that has already been converted to CMYK should then look identical to the image at the top left after converting the document.

According to my logic, Document Setup > Color > Convert is exactly the same process as in Photo Document > Convert Format / ICC Profile.

[Hangman]

Hi @PeterB.,

Not at all, I see your issue now and I'm unsure at the moment why there is a difference...

[PeterB.]

Thanks! Maybe someone at Serif can shed some light on this. By the way, would you mind telling me how you make color values appear as bubbles?

[Hangman]

5 minutes ago, PeterB. said:

Thanks! Maybe someone at Serif can shed some light on this.

I'm racking my brains trying to figure out why this is happening, it's clearly an RGB to CMYK colour conversion issue and equally a concerning one... Hopefully, someone in the moderation team can shed some light on this and log accordingly if they consider this to be a bug, which I think we have to assume it is...

6 minutes ago, PeterB. said:

By the way, would you mind telling me how you make color values appear as bubbles?

Unfortunately, this isn't an Affinity feature... I exported the file to PDF and then checked the colour values in Packzview which displays the colour value bubbles, though this would be a really nice addition to the Affinity apps along with a true colour separation view...

[PeterB.]

I tried around for ages, but couldn't for the life of me figure out what was happening.

Even according to my understanding of color management, it can only be a bug.

Let's wait and see if a team member comments.

[Callum]

Hi Peter, I've been looking into this with a member from our QA team and we are struggling to replicate this as the files you provided have missing links and the images that you pasted into your forum post have all been converted to RGB. Would you be able to provide a recipe we can follow to recreate this issue from scratch or a .zip containing the image files you are using?

[Hangman]

Hi @Callum,

I was able to create the same issue from scratch by doing the following:

1. Create a 150 mm x 150 mm, RGB/8 Designer Document using the Display P3 profile
2. Add six horizontal 150 mm x 25 mm Rectangles spaced evenly
3. Colours the rectangles as follows:
        Red R255 G0 B0, Green R0 G255 B0, Blue R0 G0 B255, Yellow R255 G255 B0, Magenta R255 G0 B255, Cyan R0 G255 B255
4. Export the file as a JPEG with the profile embedded as Colours RGB.jpg
5. Change the Document Setup to CMYK/8 using the PSO Coated v3 profile
6. Export the file as a JPEG with the profile embedded as Colours CMYK.jpg
7. Create a 300 mm x 150 mm Publisher Document using the Display P3 profile
8. Place the Colours RGB.jpg file into the Document
9. Change the Document Setup to CMYK/8 using the PSO Coated v3 profile
10. Place the Colours CMYK.jpg file alongside the Colours RGB.jpg file
11. Note how the same colours in the two files have different colour values. The only difference is that the colour conversion for the Colours CMYK.jpg file was made in Designer and the colour conversion for the Colours RGB.jpg was made in Publisher

Source Designer File and Exported JPEGs attached

 Colours.zip

[PeterB.]

Hello @Callum,

@Hangman described it in great detail, thank you for that! I just tried again, but I can no longer reproduce the behavior with version 2.4.1. Have you changed anything internally about the color behavior during conversion?

@Hangman, can you still reproduce it with 2.4.1?

[Hangman]

Hi @PeterB.,

Same issue in 2.4.1... Note: 2.4.1 doesn't contain any bug fixes...

[PeterB.]

@Hangman, have you tried it with documents and exported files created new from scratch? If I follow your step-by-step instructions, then I can no longer reproduce the result. If I use your "old" files, then I can reproduce it...

[Hangman]

Hi @PeterB.,

The ones shown in the screen recording I created from scratch yesterday so I could retest...

3 minutes ago, PeterB. said:

If I use your "old" files, then I can reproduce it...

Are you referring to the files I uploaded yesterday? If so, those are the ones created from scratch yesterday... It's a little odd that you can no longer reproduce the issue, are you using the same two ICC Profiles, i.e., Display P3 and PSO Coated v3?

[PeterB.]

18 hours ago, Hangman said:

1. Create a 150 mm x 150 mm, RGB/8 Designer Document using the Display P3 profile
2. Add six horizontal 150 mm x 25 mm Rectangles spaced evenly
3. Colours the rectangles as follows:
        Red R255 G0 B0, Green R0 G255 B0, Blue R0 G0 B255, Yellow R255 G255 B0, Magenta R255 G0 B255, Cyan R0 G255 B255
4. Export the file as a JPEG with the profile embedded as Colours RGB.jpg
5. Change the Document Setup to CMYK/8 using the PSO Coated v3 profile
6. Export the file as a JPEG with the profile embedded as Colours CMYK.jpg
7. Create a 300 mm x 150 mm Publisher Document using the Display P3 profile
8. Place the Colours RGB.jpg file into the Document
9. Change the Document Setup to CMYK/8 using the PSO Coated v3 profile
10. Place the Colours CMYK.jpg file alongside the Colours RGB.jpg file
11. Note how the same colours in the two files have different colour values. The only difference is that the colour conversion for the Colours CMYK.jpg file was made in Designer and the colour conversion for the Colours RGB.jpg was made in Publisher

Source Designer File and Exported JPEGs attached

  Colours.zip 3.4 MB · 1 download

@Hangman Yes, I used your ZIP file from yesterday and tried it. With the files I was able to reproduce it. But if I follow your instructions and do everything exactly like that, I can no longer reproduce it. I think my brain is melting and I need to leave it for a day and then start again. I've made two updates since last time. Once Affinity 2.4.1 and a MacOS update to 14.4.1... I'll try again.

[Hangman]

Hi @PeterB.,

Very strange, the instructions mirror how the files were created... I'm trying to think what could be different other than the version of macOS...

If you get to try this again later let us know how you get on... hopefully, @Callum can test as well using both the sample files and by following the instructions from scratch to see the outcome...