I have been looking at trying a couple of rolls in the dr.5 process as I prefer slides over negatives. The thing that I am having trouble getting my head around is if I am shooting Pan F iso 50 they recommend shooting it at iso 25. After reading a bunch of the different film reviews I noticed that they recommend a rather large overexposure for the films they list as good in the process. Could someone help me to understand why overexposure is desired to get BW film. Some of the suggested iso's end up with up to 2 stops OE. This might be a simple explanation but I haven't figured it out yet.