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Alex ChambersandClaude Opus 5.5
8b9a020084
Auto was a percentile rule that set Exposure about 1.4 EV higher than Lightroom's Auto on the same photos (mean +1.81 against +0.44 EV) and barely used Shadows: on 24 Sony raw photos its results were further from Lightroom's Auto results (median dE76 22.0) than leaving the photo unedited (7.9), about 18 L* too bright. Auto is now Lightroom's shape of rule with values chosen for our results: - Exposure = -0.58 - 0.41 * the scene's log-average luminance (EV from middle grey, scene-linear, under the photo's white balance, so it does not depend on the base tone curve), clamped to -2..3 EV. The slope is Lightroom's: its Auto's chosen Exposure against our log average, r -0.92; - Highlights -66 and Shadows +52: Lightroom's own average Auto values; - Contrast +68 and Vibrance +30 (our scales; our base tone is flatter); Whites, Blacks and Saturation 0. The exposure offset, Contrast and Vibrance were fitted jointly so our renders match Lightroom's Auto exports on the 16 photos whose starting look Sony's DRO doesn't brighten (#568 changes the other 8). Held out one photo at a time, each fold fitted from its own training photos only: median dE76 6.38 on those 16 (8.28 unedited, 18.81 with the old rule), 12 of 16 closer than unedited; 7.70 on all 24 (7.92 unedited); on the 8 DRO photos 9.39 (7.00 unedited), their brighter start showing through. Freeing Highlights and Shadows too (5 fitted values) did no better held out (6.51) and left them poorly determined across folds. The log average skips pixels that aren't finite (a damaged decode) through the proxy's resampling and white balance; with no valid pixel, Exposure 0. Values are black-box observations of Lightroom (the settings its Auto chose and its exports), as in #514. Auto only applies when asked for, so existing edits keep their look; HDR merges with Auto Settings use the same rule. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>