Can't this be corrected in PhotoShop?
Not unless you can construct what isn't there. Since we're talking about black and white film, the problem is not color but relative loss of film speed. Every 1/3 stop loss in film speed looses a bunch of shadow detail. This is then followed by a proportional reduction in local contrast, the small variations that make a photograph expressive. It can mean the difference in highlights that just separate from lower values and ones that scintillate.
Peace! Sidney
