I'm going to be doing a shoot of building interiors, natural light only, and its pretty dark inside. Typical exposures are in the 30 second F8 range. I was planning to use up a box of Plus X in 4x5 that I have, but don't have the reciprocity data sheet.
Will I need to lengthen the exposure time and/or increase the development at these light levels? Artifical light isn't an option, so I'm stuck with these long exposures.
I've also got some HP5 if that will work better.