Your image reversal point is a good one. It might be that it was reversed in the images, I don't really remember.

I couldn't find the photographs, but they are mentioned at some pointsin the "Battle for Chernobyl" movie: http://topdocumentaryfilms.com/the-battle-of-chernobyl/ (Highly recommended movie, btw. Very freaky.)

(Also noticed that it's at Google video. Watch it while you can!)