Inconsistent film speeds with different film batches

[William Marderness]

I finished most of my testing with HP-5+ to find various N-2 to N+1 with D-76 1: 1. All was well untill I opened a new box of HP-5+ and tested with that. I am ge tting flim speeds of about 1/2 stop slower than I got with the previous box. At first I thought my exposures or processing was the variable, but I have made 4 t ests, and the 1/2 stop loss is consistent. Is this normal between different batc hes of film?

[Ellis Vener]

You used to see it more with E-6 color materials, also different color balances as well. EPR in particular needed testing regularly, and I noticed that Fuji "tweaked" color response on velvia a few times, but this all seems to be a thing of the past now. Are you changing your stock solution of developer between tests?