Inconsistent colour rendering to pdf (RGB)

[shadowphiar]

Hi,

I'm getting some inconsistent results when using the PDF export presets such as "Digital (High Quality)" rendering a CMYK source document into RGB colour space. (Exporting to "Press Ready" does not show this issue).

In the attached example, the line and the attached box are the same colour but are displayed quite visibly different in the PDF by either Adobe Reader 21.1.20145, or MacOS Preview 10.1 (944.6.16.1). Similarly the other line and its attached circle are the same colour in the original document.

I'm using Affinity Publisher 1.9.2 on Mac OS 10.14.6.

test (digital - high quality).pdf test (press ready).pdf test.afpub

Edited April 12, 2021 by shadowphiar

[Hangman]

Hi shadowphiar,

This is in part down to the way you have specified colours in your document and also how you've subsequently exported it. Although your document is set up as CMYK U.S. Web Coated (SWOP) v2, it looks as though both the blue rectange and the pink dashed circle have colours specified using RGB colour values whereas the blue and pink lines are specified using CMYK colour values as shown below...

Subsequently when exporting using the PDF Presets, the PDF (press ready) preset embeds the document profile (by default), the PDF (digital - high quality) profile doesn't embed any colour profile (by default)... which is why you are seeing a difference in the colours, i.e. a mix of CMYK and RGB colour values.

Two options, either...

1. Change the RGB specified colours in your document to the relevant CMYK colours prior to export (if your output is required in CMYK).
2. Click 'More' under the PDF export dialogue for the PDF (digital - high quality) profile and change the Colour Space to CMYK and the Profile to 'Use document profile' or CMYK U.S. Web Coated (SWOP) v2 and tick the 'Embed profiles' check box.

If you open your exported PDF 'test (digital - high quality).pdf' in Publsiher and either set the Colour Space in the PDF Options dialogue to CMYK or simply open the file and then change the Document Colour Settings to CMYK U.S. Web Coated (SWOP) v2 then the colurs will match, although note there is a tiny discrepency between the blue line and blue rectangle in that the Cyan value is out by a value of one in the conversion which is why all the colours within the document should be specified using the same colour space.

What is the intended end use for the PDF file?

 

[shadowphiar]

14 minutes ago, Hangman said:

it looks as though both the blue rectange and the pink dashed circle have colours specified using RGB colour values whereas the blue and pink lines are specified using CMYK colour values as shown below

Ah - that's possible. I probably had drawn some of the objects and then used the colour picker tool to choose the same colour in its adjacent box. (It's a shame the colour picker hasn't specified into the same colour space, but I can understand how it might not.)

In Designer how can I tell which colour space a particular object is defined in? If I select one object and look in the Colour palette, I can choose to see the CMYK values or the RGB values, but I can't see anything telling me which are definitive for that object.

Is there a quick way to find all a document's objects that are defined in RGB? I'll probably never want there to be any. I thought there might be a warning somewhere in the Preflight checks, but if I enable all the "Image Colour" options, it still doesn't flag anything in this test document. Should I have expected it to?

25 minutes ago, Hangman said:

What is the intended end use for the PDF file?

Primarily for people to view on screens. I've prepared a CMYK file for the printers, and that is the primary output of what I'm doing, but secondarily there will also be a version downloadable on the web and I had assumed it would be better to use RGB for that (as it's roughly 25% smaller even before downsampling any of the images).

[Hangman]

3 hours ago, shadowphiar said:

In Designer how can I tell which colour space a particular object is defined in? If I select one object and look in the Colour palette, I can choose to see the CMYK values or the RGB values, but I can't see anything telling me which are definitive for that object.

As far as I'm aware, there is no option that shows whether you've defined a colour using RGB, CMYK or HSL (unless I've missed something). In my humble opinion I feel the colour slider panel 'should' automatically change to the selected colour model when an object or layer is selected or there should me something or some indicator that tells you the colour space for the selected object as it is not immediately obvious which is what your example highlights and is very easy to miss. As far as I can tell the pre-flight checker fails to highlight any discrepencies as well, though happy to be proved wrong about this.

I think this is one of the many current weaknesses of the Affinity Suites' Colour Management (there are many more issues which have been highlighted in the forums). I'm hoping that colour management will get a big overhaul in V2.0.

3 hours ago, shadowphiar said:

Primarily for people to view on screens. I've prepared a CMYK file for the printers, and that is the primary output of what I'm doing, but secondarily there will also be a version downloadable on the web and I had assumed it would be better to use RGB for that (as it's roughly 25% smaller even before downsampling any of the images).

I think again it is a case of ensuring that all graphics use the same colour space when creating rather than mixing them and either creating a version in CMYK or RGB, which means if you want to maintain the appearance of the CMYK colours for output in RGB you need to change the document colour space to RGB and then adjust the colours accordingly, so the Blue would appear as R:84, B:81, G:163 and the Pink as R:218, G:67, B:152 in your example.

Setting everything up using global colours would potentially make the process much easier, though I'd be inclined to have two versions of the file, one for print and one for screen. There is a huge difference in the size of the exported PDF files I agree.

[shadowphiar]

26 minutes ago, Hangman said:

I think again it is a case of ensuring that all graphics use the same colour space when creating

I don't disagree, but (a) I thought I already had, and (b) nothing visible in Affinity Designer told me that I had not. 

At a minimum, I think this is a feature request for a preflight check for Object colours in the wrong space.

[Trevor A]

Hello
I have a related question, but in the opposite direction.

I am preparing a book for printing and have set up the Publisher colour space as CYMK/8 US Web Coated (SWOP) v2.  I will be using images prepared in Photoshop, with the colour settings for RGB: Adobe RGB (1998) and for CYMK: US Web Coated (SWOP) v2, both marked "Preserve Embedded Profiles". 

When adding these images to the book, will Affinity Publisher automatically pick up the Photoshop CYMK settings, or do I first need to save each image as CYMK? (there are 266 of them!)

Thank you for guidance.

Trevor

[lacerto]

(...)

 

[lacerto]

(...)

[Hangman]

2 hours ago, BofG said:

On the swatch/colour panel there is a small padlock icon - turn this off (whilst having nothing selected) and then when you select an element the colour panel will change to match the colour space that element is defined in.

Haha, I always wondered what the little padlock was for, good to know and very useful... 😀

[Trevor A]

Thank you very much for these comprehensive and helpful replies.

I can see the padlock to the left of the little box that displays the colour space, but clicking on it doesn't seem to change the logo (between an open padlock and a closed one), so I don't know what setting I have.

Should the padlock logo change?  What should the default space be in my case when preparing for print (in the first instance)? CYMK?

Trevor

[Hangman]

No, the Padlock icon doesn't change, when 'unlocked' it simply shows which colour space has been used for the selected object.

Whilst the colours 'appear' identical for both elements, the purple and pink graphics are actually made from a mix of both RGB and CMYK colours which is only evident on export to PDF.

When the padlock is 'locked', selecting any graphic doesn't show the colour space used for that graphic, unlocking it (as I've just learnt) does, as (hopefully) shown below.

[lacerto]

(...)

 

[Trevor A]

Hangman

Thank you for the explanation and the graphic.

Lagarto

Thank you for the exercise.  I'll have to work through it carefully later today.

Trevor

[Trevor A]

Lagarto

I have now worked through your explanation and have been able to follow it.  Thank you for going to the trouble to do all this.

It seems to me that the logo variation for the padlock is that when it is turned on, it is on a black background; when it is turned off, the background for the logo is the same grey colour as the rest of the dialog box.  Very "subtle" (or, in other words, hard to see, on such a tiny logo!).  I will now be on the lookout for this semi-hidden clue elsewhere in the program!

Trevor