As a retoucher I am supposed to keep accurate color management. I create my ICC Monitor profiles with an X-Rites i1XT meter. The screen calibration includes a brightness adjustment to meet a desired luminosity value (I choose to work on a 120cd/m level). My issue is that apples "brightness slider" wont define a value or percentage which I could associate with my current ICC profile. If I would for instance watch a movie in full brightness I could never get back to my previous brightness settings in order to maintain my desired color accuracy!

is there a way to read out or dial in a "brightness value" (maybe trough a script?)
does anyone know about an external tool that could help me (without interfering the ICCs)

THX a lot,