Just 'looted' the Tool factory. i use the term looted very loosley, anyway have come out and my pip boy has gone super bright, nearly unreadable. it brightest in the middle, can just about make out the words as the edge. any ideas if this is a bug or if its some kind of in game thing?

Bug.

The light effect has gotten stuck for some reason. Turn your light on, turn the light off. That should fix it.

Thank you very much

Generally a quick save and reload will fix it too. Bug carried over from Fallout 3.