Originally Posted by mark
Kevin at B&S is right in that BPF is fine for alternative process work, *if you are in a lighting condition of SBR of about 6.5 or higher.*
But, if you hope to get enough contrast from BPF in a lighting condition of SBR 6 or lower my assessement is that *you can't get there from here.* In other words, there is *no* developer, however aggressive, that will produce enough contrast with BPF in low contrast lighting for an alternative process like kallitype or palladium that require a negative density range of about log 1.7. Period, regardless of how long you develop. Not with ABC Pyro 1:1:1:7, not with D-19 straight, not with D-11.
BPF has gamma infinity at about CI .93 but beyond that you just gain density with longer development. With BPF and Pyrocat 2:2:100 you reach gamma infinity of about CI .92 with about sixteen minutes of development. Further development increases overall density but not contrast.