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* Legacy Brightness/Contrast: brightness first, then contrast around 128, as in Photoshop With Use Legacy on, PhotoCraft applied contrast first and then added the brightness, so any setting that moves both sliders came out wrong: brightness +40 with contrast +30 mapped mid-grey 128 to 168, where Photoshop gives 185 (up to 17 levels darker across the midtones). Measured on Photoshop 27.11 (scripted, a gray ramp through seven settings): Photoshop adds the brightness, then scales contrast around 128/255. Contrast 80 keeps 128 at 128; the 0.5 pivot moved it to 130. With both changes every measured value matches within 1 level, on the CPU and in the GPU adjustment kernel. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Legacy B/C: brightness after contrast when contrast is lowered The corpus caught it: psd-tools' brightnesscontrast_legacy_grayscale.psd (brightness -23, contrast -26) matched Photoshop with the old order and was 6 levels off with brightness first. Photoshop adds the brightness before contrast when contrast is raised (measured: +40/+30 maps 128 to 185) and after it when contrast is lowered. The measured cases with lowered contrast had brightness 0, so they could not tell. CPU and GPU kernel (brightness after contrast goes in p0.w). The io corpus oracle is back at its floor; the 34 GPU parity tests pass. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>