Originally Posted by fhovie
The article in View Camera is incorrect in stating that Pyrocat-HD contains hydroquinone. It does not and never has so I have no idea why Steve Simmons would have said that it does.
About film speed, bear in mind that accurate comparison of the EFS of film in different developers requires fairly sophisticated testing methodology. In fact, I will go so far as to say that it is virtually impossible to measure accurately the EFS produced by a given developer without the use of sensitometry. Field tests, given the inherent inaccuracies and inconsistencies in exposing equipment (lens, shutters, etc.), lack the level of accuracy needed to make this kind of comparision. Another issue is that for the test to be reliable the films in both developers need to be developed to exactly the same effective printing density range *for the process being compared.* If they are not developed to the same CI the film that has more contrast will indicate a higher EFS.
Three things you should know about my procedures. When I carry out tests to compare EFS with a particular film/developer combination I use a light integrator to expose the film, thereby assuring accuracy in exposure to about 1/100 of a second. This eliminates the inconsistencies of field tests. Second, before I even attempt to compare EFS I determine what development time is needed to achieve the same CI, or effective printing density range with both developers. The third thing is that all of my comparisons of EFS are made based on either blue light analysis of the curves (for graded silver papers) or with UV analysis (for alternative processes).
OK, when I do the tests as above I see a slight speed increase with Pyrocat-HD over PMK, definitely not a loss of film speed. There are of course several things that could explain the discrepancy in our results. However, my own intuition on this is that if anyone is observing lower EFS values with Pyrocat-HD than with PMK the most probable explanation in my opinion is that the Pyrocat-HD and PMK comparison negatives were not developed to the same CI.
Another final issue is that all of my tests have been made with graded silver papers. VC papers respond differently to the different color stain of PMK and Pyrocat-HD and this makes it even more complicated to determine the effective CI of the comparision negatives, because with VC papers you also have to consider both the color filter being used, and the specific color sensitivity of the paper. The issue is really quite complicated and outside of the realm of my own interests since I am primarily interested in alternative printing.
Last edited by sanking; 07-25-2004 at 11:22 PM. Click to view previous post history.