I have not compared ABC and PyrocatHD for efffective film speed. However, with most films Pyrocat gives slightly higher effective film speeds than either PMK, Rollo Pyro or WD2D. The difference is greatest with PMK, least with WD2D. However, given the variations in the exact opening of lens apertures and the absolute accuracy of shutter speeds I have my doubts that one could accurately measure these differences with field tests. My own testing is done with a Metrolux integrator that provides repeatable exposures with an accuracy of 1/100 of a second.

In my opinion the major reason to consider Pyrocat-HD over ABC is the fact that pyrocatechin as a developing agent is cleaner working than pyrogallol and less likely to cause uneven staining or streaking. It is also quite inexpensive to use, especially if mixed from scratch. And Pyrocat-HD is the only staining developer that I personally would recommend for rotary processing. With rotary processing, however, I do recommend a pre-soak of 3-5 minutes.

Sandy King