I also wanted to use the Zero Image Pinhole instead of my usual Holga Pinhole. I hadn't shot much with that camera the Zero Image, so here we go.
I looked up the Portra 160 Reciprocity Curves, but even at f/235, I found that I didn't need as much exposure as the curves predicted.
Exposed 5 Seconds:
Exposed 10 Seconds:
15-30 seconds was recommended by the curves, but with a bright sun just out of view, 5-10 seconds worked better. notice below how the blue sky in the upper right washes out as exposure increases.
Exposed 15 Seconds:
Exposed 30 Seconds:
However, with the sky not in the view, the exposure time differences are not noticeable at all. We'll look at that in my next posting.