peter, you hold the same view as I do and asked the same question. The stuff is quite incredible I think, good speed, fine grain, amazing tonality andd just produces great negs every time with no fiddling. No idea whats in it, but like all Paterson devs, it is great. I am a real fan as they are cheap and hugely underappreciated. I am sticking to pyrocat HD for a while to really get some consistency, but once I have it nailed, will pick up the aculux again and try fx39, which I hear gives great speed and has superb acutance.