SUMMARY "Value" blend mode (under HSV section) should only change value. STEPS TO REPRODUCE 1. Create a layer and fill it with hsv(0, 100, 50) (a dark red color) 2. Create another layer above it, fill it with hsv(0, 0, 100) (pure white) 3. Change the top layer's blend mode to "Value" OBSERVED RESULT The blended color is hsv(0, 49.8, 100) (pink) EXPECTED RESULT The blended color is hsv(0, 100, 100) (pure red) SOFTWARE/OS VERSIONS Krita 5.0.6 probably all platforms ADDITIONAL INFORMATION I know other software has similar behavior. However, I still consider it a bug. Krita's "Value" blend mode is explicitly under "HSV" section, which implies it should change the value and value only, according to HSV color model. It shouldn't change saturation somehow. If I'd like to change lightness, I'd use "Lightness" blend mode (under HSL section). "Value" shouldn't try to be smart like this.
Gimp produces the right results, but Krita imports the psd created in gimp with luminosity instead of the hsv value blending mode, but that's because psd doesn't _have_ the value blending mode. Or, at least, Photopea doesn't. Setting the blending mode to value creates the effect you noted, so I can confirm the bug.