Archived posting to the Leica Users Group, 1997/11/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>I think Michael Hintlian is right, that atmospheric and even ground level >gamma are the biggest risk to TMZ P3200 (hence take the expiration date >very seriously). But I think I remember Ken Lassiter telling me that even >lead bags are no protection for that. Ken? > I think lead bags can help minimize against some, but not all, low energy gamma radiation. If you keep 3200 speed film in a freezer for prolonged periods of time, there may be a risk of fogging from the radioactive K-40 isotope in frozen food. In basement darkrooms, Rn-222 may also cause problems in some locations. Such background levels, over time, may fog the film. This may be worth testing with B- and gamma emitters to establish some guidelines for acceptable levels of radiation exposure to high speed films. No doubt someone has already done this, and literature may be available on the subject. High altitude exposure and X-ray machines are undoubtedly more serious concerns. However, it certainly wouldn't hurt to store P3200 in lead bags even when not travelling. - -GH