"Refine Edges" making selection worse?

[tothika]

Hey there,

I've been having some issues with the "Refine Edges" tool when it comes to selections. After carefully selecting my subject in the picture, I intended to refine my selection when I noticed that as soon as I clicked on the "Refine..." button, the edges of my selection became fuzzy and inaccurate right away, making my overall selection much worse. This happened without even altering the settings or painting with the brush. After spending plenty of time trying to refine the selection with the help of the "foreground" and "background" brushes the result was not much improved, so I had to resort to Photoshop in order to get the job done.

Here you can clearly see the what happens:

Now I'm aware of the low contrast in some of the edges which make the task more complicated, something moderators keep mentioning in similar posts forgetting that's often the case in real-life scenarios. However when I managed to get a nearly perfect selection on Photoshop, I realised that was just an excuse (not to mention the improvement "Decontaminate colors" makes, a feature currently lacking in Affinity Photo).

You can find the original image and my results in Photoshop as a comparison below, as well as the .afphoto file with the original selection saved as a Spare Channel, in case you want to give it a try. I've seen several posts regarding this issue, but since no actual solutions where provided and the topics were just forgotten (as you can see here, here and here), I decided to post about it myself before having to unfortunately switch back to Photoshop for good.

picture.afphoto

[James Ritson]

7 minutes ago, tothika said:

(not to mention the improvement "Decontaminate colors" makes, a feature currently lacking in Affinity Photo).

Just to point something out—colour decontamination is actually applied to the previews (Overlay, Black/White and Transparent) and carries across when you output as a New layer or New layer with mask. You should always use one of these two options for cutouts/foreground extraction. Outputting to a selection or mask will forego colour decontamination because they don't alter the pixel content.

Could I ask what your source file for this document was? I'm noticing some blocking and compression artefacting especially around the edges of the subject, suggesting the original image was quite noisy and was then compressed—not making excuses, it simply appears that Affinity Photo's selection refinement doesn't cope too well with compression artefacting.

Hopefully the support team can take a more detailed look at this in the coming week!

[tothika]

6 minutes ago, James Ritson said:

Just to point something out—colour decontamination is actually applied to the previews (Overlay, Black/White and Transparent) and carries across when you output as a New layer or New layer with mask. You should always use one of these two options for cutouts/foreground extraction. Outputting to a selection or mask will forego colour decontamination because they don't alter the pixel content.

Thanks for the info James, I wasn't aware of that hidden trick!

Regarding my source image, I only have the provided 3456×5184 .jpg file as it was part of an assignment where I had to clip the kid into a different background. So the issue for Affinity might as well be compression as you point out. You reckon this would not happen with a higher quality .RAW file for instance?