Thorston: My approach would be to meter a gray card... 1 side Z5, the other Z8, near and in front of the camera. If possible also meter a nearby light source... street lamp, and see where the EV falls relative to Z8. Base the exposure on the gray card Z5 meter value. If too low use the Z8 value. Shoot 3 or more negs at various exposures by altering (lower) film speed to maintain DoF.