[Affinity Immediately Undoes Sharpen Preview]

OK, it looks like the answer is that distorted rendering of the "after" image when the zoom factor is less than 100% causes the "issue" I was seeing.  Here is a screen shot of the same image at 100% zoom (and yes, I should have tried that first 😞).  Anyway, I think I understand what it's doing and I can deal with that now that it seems clear what's happening.  Thanks to all for the help, and again, sorry for not having tried the zoom factor first.

 

Gary 

[Affinity Immediately Undoes Sharpen Preview]

Here is a screen shot of the layer stack.

[Affinity Immediately Undoes Sharpen Preview]

MacOS 12.3.1, Affinity Photo 1.10.5.

I have a jpeg image I exported from a PDF file.  I want to sharpen the image to enhance the line darkness.  I select "select all" and then Filters > Sharpen >  Unsharp Mask and play with the sliders.  The preview it gives me is perfect.  Exactly what I want.  Unfortunately, when I click "Apply" from the unsharp dialog, the image reverts back to what it had been.  I can only assume there's something about the image format (color depth, mode, etc.) that doesn't allow my changes to stay put.  Any ideas on this?

Thanks.