First of all, TMY100 was specifically engineered for this particular application in the first place (among numerous other features intended to replace several previous films). It has a very long straight line, correctly balanced spectral sensitivity, and is the only film I am aware of where, if one calibrates the 3 exposures correctly, is capable of having all three attain the same contrast gamma when developed together for the same length of time. A LOT of testing work and densitometer plotting has to go up front to learn to properly balance a set of negatives. Of course, on forums like this you're going to encounter plenty of fun stuff that isn't fussy in that regard, or else has been twisted and bludgeoned half to death via software to make the different separations sorta get along. But it is possible to do it well via totally darkroom workflow, just like it was routinely done countless thousands of times in the past when this was the routine mode of color reproduction. HP5 has none of the characteristics I described above...[...]... Typical color separation filter sets would include 25 red, 47 blue, and 58 green. A more precise but slower exposing set of even deeper filters would be 29 red, 47B blue, and 61 green.