In a freecycle lot, I got a handfull of HP5 and Fp4 and some miscellaneous kodak films. However, one roll is labeled B&W develop in c-41 not in B&W chemicals. What is this? Is it just black and white but no color dyes in it? Ore are there black dyes? Certainly an interesting idea, but this is the first I am seeing it. Kind of a b&w for people that don't develop their own perhaps?