I tried FX1 a couple of years ago, before my unexpected hiatus on photo activity. My observations at the time:(posted 8629 days ago)a/ very,very economical - how about 1 UK pence per film dev cost? b/ up to a half-to-1 stop increase in "speed" (both claimed and observed, but I have yet to confirm it densitometrically) This strangely holds true only for slower films speeds (anyone?) c/ Acutance (perceived sharpness)is high, or at least noticeable compared with everything else I have used in the past d/ the resulting neg is quite high in contrast, with nice clean highlights, without being difficult to print, courtesy of the semi- compensating action e/ handy for street photography. The result "looks" sharper(acutance effect), more accurately exposed(compensation),more snappilly printed (the "soot and whitewash effect"),economical(for bulk film burners). I used FP4 instead of my normal HP5+D76 street combo
I wonder why it isn't more popular? I currently have 10x30metres of unbranded 100ISO neg stock in the freezer and a box of raw chemicals waiting for a fortnight of experimentation, if I can find the time. Speaking of times, my notes say (at 20C): FP4 - 12-14 mins, APX25 13mins. I have heard that most films need from 12-18 minutes in FX1 at 20C, so it could be that you can combine different film types in the same tank.
PS it needs to be stored in the dark to last. Use a dark bottle or wrap bottle in a black plastic bag.