Hi List members Just an update. We are seeing the same problem i outlined before with i1Profiler 1.7.2 and os10.13..3, but now also on our mid 2015 iMacs (model 15.1). So it’s now looking more like this is an OS issue and less like a machine specific related bug as we first thought. We tested a clean install of OS 10.13.3 on a clean partition with no addition components added to OS on a mid 2015 iMac. We then installed i1Profiler 1.7.2 and tested it. Summary 1: If the initial iMac display brightness is set to 100, i1Profiler ’s automatic display brightness control (ADC) works. But the display brightness jumps back to 100 during i1Profilers verify step at the very end. So ADC not in a usable state with OS10.13.3 at this time. 2: Manual brightness adjustment. The system Display preference pane cannot be bought forward while i1Profilers measurements pane is active in OS 10.13..3 so the brightness slider cannot be adjusted this way. As a work around you can hit the back button to get out of i1Profilers measuremnet pane. Open the Stystem display preferences and guesstimate an adjustment for the brightness slider. Relaunch i1Profilers measurement pane and look at the updated Display reading. Keep iterating this process till you reach the target brightness. XRite are seeing the same issue and are in the process of resolving this problem. Our software engineers are in the process of reporting what they are finding to the apple developers bug page. regards Peter Miles