Color shift when exporting to PDF

[Folox]

Hi guys,

I'm currently having strange color shifts when exporting from Affinity Publisher into PDF. The color of the imported RGB .jpg image is strongly shifted close to grayscale when the document is being exported, even if the used gradiation curve layer (for matching the target color space) is only slightly affecting the overall colors of the image. When exporting the pages as .jpg with CMYK format this color shift is not visible.

For better understand of the effect, I attached three images:

• 1st image: screenshot of page within Affinity Publisher without softproof
• 2nd image: screenshot of page within Affinity Publisher with softproof
• 3rd image: screenshot of the exported pdf opened in Acrobat Reader DC (but I get the same behavior also in other PDF readers and even when reopening the pdf in Publisher)

I'm exporting into ISO coated v2 300% (ECI) color space. In publisher I'm using the corresponding preflight for softproof and disabling the softproof layer before export. The behavior seems not to be dependent on the selected PDF compatibly version (I'm using PDF/X-3:2003).

I'm using Publisher 1.8.4 under Catalina 10.15.7.

Many thanks for your help!

[Gabe]

Hi @Folox,

Can you attach the afpub file in question please? 

[Folox]

Hi @Gabe,

Thank you for taking the time to discuss this issue. 
I  attached the afpub file that cause the described behavior.

PDFexport_color_debug.afpub

[lepr]

Adjustments produce significantly different results in RGB versus CMYK colour modes.

When you soft proof the RGB document, compositing is done in RGB mode.

When exporting a CMYK JPEG, compositing is done in RGB mode and then the result is converted to CMYK and exported.

However, The PDF exporting process is first converting the RGB document to CMYK and then compositing and exporting.

[thomaso]

> The PDF exporting process is first converting the RGB document to CMYK and then compositing and exporting.

Generally it is more convenient to work for print (CMYK) in the according color space (and profile possibly) to avoid such surprises.

But, fortunately, here you can influence the order of these color calculations by grouping the adjustments. (I forgot the principle rules, it has to do with the next parent layer, maybe someone else may shed more light on this). So, for instance this layer setting seems to achieve on PDF export (print preset) a definitely closer CMYK result with the RGB content:

 

[Folox]

Thanks for your reply guys. Offering the StudioLink I hoped to avoid CMYK conversion and Adjustment Layer changes on the reference picture before importing it into Publisher...

 

As you said: > The PDF exporting process is first converting the RGB document to CMYK and then compositing and exporting.

For comparison of the different export routes I also tried to export the same document to JPG considering the conversion into sRGB and CMYK. The results are much more similar than the PDF export.

It seems, that in the case of JPG export, Publisher applies the Adjustment Layers onto the RGB picture before converting into CMYK. In case of PDF export the RGB picture is converted into CMYK first, and afterwards applying the Adjustment Layers. In contrast the preview and softproof inside of Publisher always considers the layers from bottom to top and in my case adds the CMYK softproof conversion at the end.

So wouldn‘t it make sense to apply the same processing route for all export formats and the preview inside of Affinity Publisher?

Edited October 15, 2020 by Folox

[thomaso]

6 hours ago, Folox said:

I hoped to avoid CMYK conversion and Adjustment Layer changes on the reference picture before importing it into Publisher

That's fine and I prefer to handle it the same way, too. Inspite there are other users who strictly recommend to convert every resource to CMYK before using it in APub, simply to avoid unexpected results on export, and being aware of disadvantages, as larger file sizes and possibly multiple CMYK conversion in case of a different required PDF profile.

6 hours ago, Folox said:

So wouldn‘t it make sense to apply the same processing route for all export formats and the preview inside of Affinity Publisher?

Consider that the specification of the PDF format allows to maintain various layout parts as separate objects, so for instance image data separated from color mixing layout settings (PDF term: 'transparency'). As you can read in the "Objektinspektor" in my recent screenhot the PDF contains 4 objects (as kind of 'layers'): 3 images in CMYK + 1 "Mischfarbraum" in sRGB – whereas a JPG doesn't have this flexibility and contains a plain pixel 'layer' only. In this case APub has no chance to influence the order of color mixing in the exported PDF.

Simply spoken the complexity of the app may satisfy professional users and their need for custom flexibility but results in an increased number of options, setting variants & possible confusion. So, alternatively the question could be: Wouldn't it make sense...
... to export as JPG and put the result in a PDF container? (to use a simple way)
... to use the .afpub color space according to the export color space? (to use a reasonible workflow)
... to change the order of adjustment layers according to the expected results? (it seems just moving the "Curves" adjustment layer only is sufficient – no group layer needed. Make it a direct child of the Picture Frame, not as secondary child nested within the image)

... to use, within a RGB .afpub, the "Curves" adjustment option to become set in CMYK not RGB?
Already just this small change results in a quite close PDF output. Compare the different adjustment histograms which might kind of 'preview' the unexpected desaturation of your first result:

...  

[Gabe]

Only PDF/X1 is affected by the wrong order (it's not that obvious in your case). So, what you see in your X3 is correct.