Missing basic tutorials. Is Affinity a prepress tool?

[thomaso]

9 hours ago, Petr Stanicek said:

Common, this makes no sense at all…

An original background pixel has a 4% of yellow. The RGB values seem plausible (even if Color Meter shows slightly different value).

Then Highlights are applied. The background color becomes visibly brighter, Color Meter shows almost white – but APhoto says 12% yellow. 🤯😵🤪

This must be a bug, right?

Apple's Digital Colour Meter appears to report (measure, calculate) not exactly the same than APhoto does in its Info panel, especially if the meter.app is set to "native". For APhoto the assigned colour profile appears to matter differently than for the meter.app. Note that the meter.app mentions the monitor profile whereas APhoto tells the currently assigned image profile. – For instance:

sRGB –> sRGB:

native –> sRGB:

native –> ProPhoto:

sRGB –> ProPhoto:

[thomaso]

6 hours ago, NotMyFault said:

Ok if i object? If you allow to use a combination of 2-3 adjustments, or blend range, you can transform selected color ranges into transparency.

• channels mixer can do that. 

Ah, thank you for clarifying! –  My post was imprecise related to the OP's hint "just about adjusting the white point…", which would not create the required transparency.

13 hours ago, Petr Stanicek said:

FYI, the background color is mostly CMYK 0-0-5-0, so it's maybe just about adjusting the white point…

[thomaso]

9 hours ago, Petr Stanicek said:

Highlights are applied. The background color becomes visibly brighter

Your sample screenshots appear to use a different image, also I guess you are using different image resolution which would have more details than the uploaded JPG available for us to experiment with. Aside that it appears I can achieve your mentioned 0 / 0 / 0 / 0 cmyk with a highlight adjustment of 6 %. (it may vary slightly for your original image). Consider that for such low, subtle CMYK values the profile of the book layout document, respectively the exported print PDF will matter (respectively profile conversion during pre-press), so values like 0 / 1 / 1 / 0 (or, e.g. RGB 255 / 255 / 254) might not appear on a print at all.

BTW: A White Balance adjustment doesn't brighten that much but rather reduces saturation (while I agree, different than expected I am unable in Affinity to achieve a neutral white this way, too, in particular when using the picker only)

It might help if you set samplers in the info panel (as mentioned by @v_kyr). This ensures to measure the exact same spots across the entire procedure. Since your image may have higher resolution than your forum upload it may matter even more because the paper background is not an homogenous colour.

No adjustment yet, Two samplers (left CMYK, right RGB):

Highlight adjustment +6%:
Without a limiting pixel selection (mask) it reduces highlights in the illustration, too.

You can add more samplers with the burger menu, and might need to increase the panel height to make the visible. A new sampler appears in the upper left corner, to place it you need to zoom out and move it with the Move Tool.

[Petr Stanicek]

5 hours ago, Dazmondo77 said:

just thought I'd share my workflow which details how I now deal with this sort of thing

Thanks a lot, yes, it seems to be usable method. I'm just struggling with the nonsense color values the Info panel shows to me (as above) – if I can't solve/fix that, I'm affraid I can't use of the suggested methods…  

[Petr Stanicek]

2 hours ago, thomaso said:

Apple's Digital Colour Meter appears to report (measure, calculate) not exactly the same than APhoto does in its Info panel…

I know that @thomaso, but that's not the point. You can see it even on the screenshots – with Highlights on, the background color is noticably brighter, almost white, but the Info panel says it's even more yellow Y=4 → Y=12. That's the problem. The difference betweeen native RGB values shown by ColorMeter is like the RGB 254–253–256 vs 254–253–257 difference. This Y=12% (or RGB 253–251–232 vs RGB 255–255–251) is a huge difference, and it's a pure nonsense. A bug, I guess.

See this – I added a square with real CMYK 0-1-12-0 which Info identifies the background. The Hightlights adjustment is applied to the background only. 😱

[thomaso]

1 hour ago, Petr Stanicek said:

See this – I added a square with real CMYK 0-1-12-0 which Info identifies the background. The Hightlights adjustment is applied to the background only.

Indeed strange that Info reports the same values for both spots in your file. I can't reproduce it here. – What highlight adjustment did you use + what document colour space/profile?

This leads me to a problem of CMYK values in an RGB document.
See below the difference between the applied 0-1-12-0 versus the Info 1-1-11-0.

This effect gets more visible with a colour which isn't directly part of the document's RGB space.
Below both samplers target the same colour. Note the difference between the two CMYK values in the Colours panel versus Info panel: 0-1-100-0 –> 3-3-82-0

This gets really weird if I convert this .afphoto from RGB to CMYK. Then the values for the fill color are equal 0-1-12-0 in both panels but the highlight-adjusted colour & its value go crazy, displaying a darker colour with a brighter value of 0-0-2-0:

Yes, currently I agree, this feels quite buggy.

[Petr Stanicek]

I'm affraid I can't rely on such a buggy thing with my book. I'm not happy, but I'm going to buy Photoshop again…