i shoot alot of pinhole photos so reciprocity is familiar. i tried the efke 25 film the other day http://www.f295.org/Pinholeforum/for...ghlight-/#num0 for a linkto my question.
i suggest you download and use the pinhole designer http://www.pinhole.cz/ this is really great, and very helpful. it was suggested that efke 25 is about the same as TMX 400, so you can plug in your info and it will create a chart for you to determine your exposure. i found te chart to be very close. i hope this helps.