I have a lot if friends who work with hot glass, mostly torch work. They use didymium glasses so that they can "see" the flame. It's purple glass that cuts out the yellow/orange glare. I know I can get didymium plates that could hold in front of my camera, but is there an actual didy filter that I can put in my hassleblad? How would such a filter reproduce on a B&W negative? I'm wanting up photograph a friend while he works pretty soon.