I remember when the first C41 B&W film came out. I think it was Ilford XP1 back in the early 1980's. It made shooting 35mm for other than street an very viable options in that it had a nice tight grain and a lot of speed latitude and could be shot from ISO 100 to ISO 800 and held together really well and kept the tight grain structure. Then XP2 could be pushed on up to ISO 1600 with no problems. The real beauty was you could expose a half a roll at ISO100 and 1/4 of the same roll at ISO 800 and the rest at ISO 400 and just have it developed. The ISO 400 rating was really just a suggestion. Really flexible. After about 1985 the only 35 mm film I used was XP. Dang this conversation makes me want to dust off my M4 and get the shutter recalibrated and head out with it.