Quote Originally Posted by Jim Noel View Post
the results of a blue filter with panchromatic film come close but are not identical to those of orthochromatic film.
You certainly have a point here as the sensitivity added to the silverhalide through the sensitizing dyes will hardly ever exactly match the spectrum removed by filtration. If done right it can be done but if you want to have the same exact effect as using ortho, using the right film is certainly more straightforward.

This reminds me of my experiences with using tungsten film which I could never quite match by using daylight fim and filtration, but I could get close.