film speed

hi
i just finnished my new film speed test using a slosh tray from PF for 6 4X5 sheets in PMK pyro. using my old system of yankee tank insert dunked in a 3qt container my fielm speed was iso 200 w hp5+. it now showes a iso of 800 is this strange.? most people have lower film speeds not higher.
thanks
mitch

Are you sure this is ISO? ISO determination requires a particular procedure. It will depend on contrast, which will depend on agitation and other factors.

This is probably too high for hp5. My speeds in PMK and Pyrocat are at 400. I'm not sure what process you are using to determine film speed. I shoot a grey card and expose at different speeds. Then process normally and read the exposures on a densitometer. The density that is about .1 above base+ fog determines film speed for the film/developer combination. You can then tweek development times to produce a ZV exposure (18% grey card) at about .65 + B+F density.
This was the original approach AA used when establishing the Zone system. There are several variations, but the original method has always worked well for me.