I recently started having a problem with long exposure (30 sec +) photos having a pattern of red noise. The problem started in the middle of a camping trip - long exposure pictures looked fine one night, and a couple nights later they looked like this (f/3.5, 72 sec, ISO-1600, D7000, Nikkor 18-200 f3.5-5.6):
I've narrowed down the problem to be related to the specific lens - here's a picture I took upon returning home using the same lens (lens cap on, view finder covered). You can see the same red noise pattern (f/3.5, 30 sec, ISO-1600, D7000, Nikkor 18-200 f3.5-5.6):
Any ideas what's going on? Is my lens damaged somehow? My first thought was that the mount was bent and letting light into the sensor somehow, but the pattern seems very consistent regardless of the camera's orientation relative to external light sources. I'm baffled.