On an IBM P275 I have controls for contrast, brightness, individual RGB contrast and individual RGB brightness. Of the individual controls, which is equivalent to RGB gain & offset in dispcal? And what are the best practise settings to begin tuning the calibration from? For example the general controls usually are max contrast and minimum brightness. On a related note, if I repeat the black level portion of dispcal it wants me to go lower with each iteration despite meeting it's target each time. Is this just trying to get to a level of 0 limited by the default -k factor? Is there a level I should be aiming for short of pure black?