In the last weeks I shot raw files (ORF; Olympus UZ570)and first used ACR 4.4.1. Auto Tone option. Later on I used ACR 4.5 on the same files and noted that especially the brightness was substantially different after using Auto Tone; other values were hardly affected. Typical example a brightness value of 53 with ACR 4.4.1 changed to 6 in ACR 4.5
This behaviour results in regularly under-exposed pictures.
I've always been curious about this. Is auto-tone a one-time thing or will an engine with different
algorithms apply different auto-toning retroactively? Seems like the former is preferred but I've
never known for sure.