When you're using PMK pyro and doing zone system tests, it's my understanding th at the densitometer readings are taken with the blue filter in place (i.e. you n eed a color densitometer). Fortunately, I have a color densitometer. However, I' m not clear on exactly what the blue filter accomplishes. Is it supposed to "rea d through" the pyro stain, so that in theory at least the numbers you get with p yro would approximate the numbers you would get with a normal developer? I ask t he question in part because as I've started doing the tests, I've gotten very hi gh base plus fog numbers with devleopment times of 8 minutes or more, much highe r than the numbers I got with times of 4 minutes and 5 1/2 minutes (I use Phil D avis' testing system, not "traditional" zone system methods). This despite takin g the readings with the blue filter in place on my Macbeth color densitometer. I realize that base plus fog increases to some extent as development times increa se but the difference here is much greater than anything I've seen using develop ers other than pyro. Since there is no exposure given to the base plus fog area of the film, I can only assume that the increase is caused by the increased stai ning as the development times increase but I thought the blue filter was suppose d to more or less allow the staining to be ignored. If it does, then why is the base plus fog increasing so much?
As an aside, the color wheel on my densitometer has two sides with identical col ors on each side. The only difference is that on one side the letter "A" is next to the three colors. The instructions don't say anything about what the letter "A" stands for or what the difference is between the two sides of the color whee l. Does anyone happen to know?