Plus X reciprocity

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.

Craig

Kodak PDF here:
http://www.kodak.com/global/en/professional/support/techPubs/f8/f8.pdf

If Indicated
Exposure
Time Is
(Seconds)
Use This
Lens-
Aperture
Adjustment
OR
This
Adjusted
Exposure
Time
(Seconds)
AND
Use This
Development
Adjustment

Indicated exp Adjust by or expose by and develop adjust:
1/100,000 +1 stop Adjust aperture +20%
1/10,000 +1⁄2 stop Adjust aperture +15%
1/1,000 None None +10%
1/100 None None None
1/10 None None None
1 +1 stop 2 –10%
10 +2 stops 50 –20%
100 +3 stops 1200 –30%

Exactly what I need, thanks!

Craig said:

... and/or increase the development at these light levels?
Craig

Click to expand...

Craig,
Notice that for increasing exposure times over 1 sec. you will decrease, not increase, the development. Contrast inherently increases with the exposure time, so you counteract that with minus development.