When holding down Alt and drag the highlight and black level sliders I'm used to seeing the pixels which will be pushed to white or black displayed on a black background.
This no longer happens on my Powerbook. I've just swapped a 17" 1GHz PB for a 12" 1GHz, but I can't see how that could have affected anything. If it's of any help I have a Bluetooth Apple keyboard.
Anyone else had this functionality vanish?
<edit>typo