The light sensors adjust the display brightness with the brightness knobs at all settings. The detent is not auto, simply a mid position. The knobs provide pilot control of the display intensity over and above the auto brightness ie turn the brightness to 3/4 and it will still vary with the ambient conditions but at a brighter overall setting than in the mid detent position. The technical manual does not state that the detent is an auto position, at least not in the manuals I have!