Using an adjustment layer seems to decrease resolution in PDF Export

[AzureiP]

Hi,

I use Affinity Publisher to arrange some images on a page for print. The plan is to export this page as PDF and send it out for printing to a print shop.

The print shop prints always a bit too dark, so I use an adjustment layer to brighten up the images. One layer and under it all images on my page.

Today I noticed a strange behaviour. If I disable the adjustment layer by klicking on the gray dot, the exported PDF is less pixelated compared to an export with the adjustment layer on. So it looks to me that I loose resolution if I enable the adjustment layer. I double checked that the export dpi is the same for both exports.

See screenshot 1 of a PDF file with the layer on, the images is brightened and more pixelated. See screenshot 2 of a PDF where the layer is off. See screenshot 3 of my layeras, the adjustment layer currently disabeled.

Can someone reproduce this? I also noticed that during PDF export: If the layer is off I see the progressbar during export as the program renders the images one by one, i think. And if the layer is on, the bar is 0% and then after a while the export is completed. No progress is visibla at the export progress bar during the export.

 

[GarryP]

I just did a quick test, adding a basic Curves Adjustment to the page of a document and then exporting the document to PDF, with and without the Adjustment applied, and I’m not seeing any pixelation created by using the Adjustment.

I’m seeing some ‘smudging’ where the colours are similar but that might be expected.

Would you be able to share the document (or a cut-down version which exhibits the same behaviour) and a screenshot of your export settings?

[AzureiP]

I created a project with bundeled images. In my testing it can reproduce the issue. Export it two times with my PDF settings from the screenshot. With the adjustment layer enabled and with the layer disabled. Than zoom into the PDF and compare the resolution of the spines of the palm tree.

bug test.afpub

[lacerto]

I can reproduce decrease of resolution. When using the adjustment with same specs will result in conversion RGB images to one CMYK image the resolution of which is 93.187 ppi, while when exporting the image without adjustment applied will have the specific appr. 150 ppi retained in each image, retained in RGB color mode.

[AzureiP]

Great that you can reproduce the problem. Can you make an internal bug Issue and write a post in this thread once an update is available?
What do you mean with your last words? "retained in RGB color mode"
It is an cmyk color project. Are the images in the PDF not in CMYK in both export cases?

[walt.farrell]

47 minutes ago, AzureiP said:

Great that you can reproduce the problem. Can you make an internal bug Issue and write a post in this thread once an update is available?

Lacerto is just another user. What you ask will require the involvement of someone from Serif when they get to this topic.

[AzureiP]

Ok, in my opinion this is required here.

[pbasdf]

Having looked at the PDFs produced with different settings, I think the issue might be related to the dimensions of your page, ie. very wide. It looks like Affinity composes a single 'image' from all the images and then applies the Curves Adjustment to that one image. But I think that image is so wide it exceeds some internal limit (16384). The DPI is adjusted so that the 'image' is max 16384px wide. That's my guess as to what's happening.

If it helps for your situation: if you apply the Curves adjustment to each image layer separately, then the result is seven separate images each at 150 dpi.

 

 

 

[lacerto]

16 hours ago, AzureiP said:

It is an cmyk color project. Are the images in the PDF not in CMYK in both export cases?

The images, however, are in RGB color mode. When you export using PDF/X-3 (or within Affinity apps, basically using anything else than PDF/X-1a:2003) placed RGB images can be left in RGB color mode (while native RGB colors of shapes and texts are always converted to CMYK, even when PDF version itself would allow mixed color spaces). Whether they are converted, is basically dependent on whether "Convert image color spaces" PDF export option is used. But when you apply an adjustment, it seems that CMYK conversion is forced, and it seems that when an adjustment is applied on multiple images, the separate images are first merged into one big image, and as mentioned above by @pbasdf, there appears to be an internal limit that triggers decrease of resolution to avoid very large images. It would be possible to retain the image resolution also in such cases by applying the adjustment separately for each image.

[AzureiP]

I checked both exported PDFs with Adobe Acrobat Pro and in my case in both version were the images in CMYK. So "Convert image color spaces" works as expected.

I now understand what happens and how to bypass the problem. But I wish that the maximal resolution of a group is increased in further versions. I use the publisher software to place images on a roll print and wondered why the images are not sharp. After paying fo unusable prints and some investigation I discovered this issue. Maybe Adobe software is still a better option for me...