Thank you all for your helpful comments.
Keith in your example of severe overexposure, you said your negatives was almost black. In normal circumstances to salvage this you need to do some special printing procedures isn't it? But if you just scan it on the computer I presume it would be almost black with almost zero detail right? My understanding is that the latitude advantage of black and white film is manipulated in the traditional developing and printing process but not in the scanner procedure.