Images with shadow/light adjust in CMYK document export burned on RGB PDF

[Daniel Gibert]

Hello.

When exporting to RGB PDF from a CMYK document with images with shadow/light adjustment, the final result in PDF is burned images. Exporting to X1A or any other CMYK setting works well. It seems like an error on converting to RGB.

I've attached the Publisher document and the incorrect pdf export.

Steps to reproduce:

• Insert image, trim it and apply a shadow/light correction adjustment (Tried both linked an embedded)
• Export to cmyk pdf: exports correctly
• Export to RGB pdf: images appear extremely burned.

rgb export.pdf rgb export issue.afpub

[NotMyFault]

It seems shadow & highlight adjustment is not adapted to CMYK model. It increases the brightness of lighter pixels, which gets opposite effect in case of CMYK subtractive color model.

As a workaround, you could use exposure adjustment, and use blend range to limit its impact to the brighter parts.

Can't say if the behaviour of S&H is a bug or by design.

[Dan C]

Hi @Daniel Gibert,

Thanks for your report!

I believe the application is behaving as expected here - the image files you have placed are RGB, in a CMYK document. When exporting to an RGB PDF, the adjustments are applied to the image after the colour conversion. Meaning your RGB images are converted to CMYK in the app for preview, then 'unconverted' (so to speak) when you export to RGB PDF. 

The same results can be seen if you copy and paste the image layer from your CMYK document to an RGB document - with your adjustment at 200% value, the image is blown out in RGB -

I hope this clears things up

[Daniel Gibert]

On 2/3/2022 at 3:02 PM, Dan C said:

Hi @Daniel Gibert,

Thanks for your report!

I believe the application is behaving as expected here - the image files you have placed are RGB, in a CMYK document. When exporting to an RGB PDF, the adjustments are applied to the image after the colour conversion. Meaning your RGB images are converted to CMYK in the app for preview, then 'unconverted' (so to speak) when you export to RGB PDF. 

The same results can be seen if you copy and paste the image layer from your CMYK document to an RGB document - with your adjustment at 200% value, the image is blown out in RGB -

I hope this clears things up

Hi Dan C. Thanks for the information.

I understand the process and now I know what to expect. Anyway, this is a horrible behaviour for the PDF output, because it destroys completely the WYSIWYG. If Publisher is able to calculate a CMYK preview, and export a correct CMYK PDF for that adjusted RGB image, it should also be able to correctly convert to RGB that same CMYK output. (And viceversa) This is something that is could have a good improvement on the future.

I'll cope with it, but i find it somehow wrong. Fortunately is something that does not happen frequently on the type of work I do. Rarely apply color correction directly as adjust in Publisher, I normally process the images in photo persona. Just a case on which I needed to do it as layer adjust and export on RGB and CMYK. 

Thanks for explaining it anyway.

[thomaso]

6 hours ago, Daniel Gibert said:

this is a horrible behaviour for the PDF output, because it destroys completely the WYSIWYG. If Publisher is able to calculate a CMYK preview, and export a correct CMYK PDF for that adjusted RGB image, it should also be able to correctly convert to RGB that same CMYK output.

It has nothing to do with PDF export. It is related to different color spaces, as colors also visually change if you switch your layout document's color space from RGB to CMYK or vice versa, some colors more obvious, others less. Especially for color affecting adjustments or filters I would not expect an identical appearance in RGB versus CMYK, like I would not for certain Layer Blend Modes, too. Their different appearance is sort of 'wanted' to get additive vs subtractice colours handled, respectively CMYK 3 channels + 1 Back merged to 3 channels RGB. – WYSIWYG is not meant to eliminate this differences between color spaces.