Created attachment 185917 [details] Blur disabled on the left, and enabled on the right. SUMMARY In Plasma 6.5 betas as well as Neon unstable (6.6), the blur effect is broken. It appears to add brightness to the content behind it. STEPS TO REPRODUCE 1. Enable Blur effect 2. Make menus transparent 3. View menus or shutdown/logoff background OBSERVED RESULT Blurred content appears way brighter than normal. EXPECTED RESULT No brightness should be added. SOFTWARE/OS VERSIONS KDE Plasma Version: 6.4.91+ KDE Frameworks Version: 6.18.0+ Qt Version: 6.9.0+ ADDITIONAL INFORMATION Screenshots are from a fresh install of KDE Neon Unstable. In Application Style->Breeze, I set Transparency to full. In Desktop Effects->Blur, I set Blur and Noise strength to Light (though other settings do not alleviate the issue). I also tested Kubuntu Beta PPA as well as my own kde-builder Plasma install, which both looked the same. CPU is a Ryzen 5600x. GPU is a Radeon 6700 XT.
Created attachment 186005 [details] Blur effect on 6.4 / 6.5 I can confirm that the blur effect appears different in Plasma 6.5. The attached image shows a comparison of Yakuake with translucency and blur enabled. In Plasma 6.5, the blur effect looks noticeably brighter and more saturated compared to Plasma 6.4.
Created attachment 186012 [details] Merged screenshots of blur on and off I can also confirm. Here's 2 screenshots (merged into 1 image) of the color when blur is enabled and when it's disabled.
The blur and background contrast effects got merged in 6.5
Poked around the kwin code, and apparently early code changes had an option to disable the forced contrast, but they removed it: https://invent.kde.org/plasma/kwin/-/commit/ddc7f8f123a1cf0be9724e1e10296a5138970272 It would've been nice to at least have a hidden kwinrc setting we could tweak. I hope they'll reconsider.
Created attachment 186043 [details] kwin v6.5.0 patch to add "Use contrast settings" option to blur plugin Apply this patch to kwin to add a "Use contrast settings" option to the blur plugin.
I made a bug rapport about this before I see this bug rapport https://bugs.kde.org/show_bug.cgi?id=510903 I don't at all recognize kde/plasma in this change. Imho the whole thing became ugly and there is no choice.
Can reproduce Feren OS's Plasma Style always opted out of the contrast effect in its Plasma Style because the contrast effect caused it to be brightened to a dark grey instead of black, which looks ugly. Especially in its upcoming Inspire 4.0 design where there is more established borders around Plasma elements, the contrast effect is not needed, makes the theme ultimately look worse than without due to the aforementioned brightening of the theme that isn't desired, and should be able to opt out of contrast again. Inspire never needed neither brightening contrast nor darkening contrast due to the fact it's designed to be its own contrast-substitute - I apologise for not raising this in the merge request as I missed it, but I really do need this option back.
I also want to express my dissatisfaction with the way this contrast setting looks and the inability to disable it. Please consider adding the toggle back in :).