Rule number 1: Know your equipment!
I just came back from an hour long trip in the cold darkness of a nighttime city. Finally, I got myself a tripod for an early birthday present and was eager to give it a try, with a few ideas for some night shots in my mind. Instead of filling my memory card with awesome photos, however, I ended up fiddling with camera in the dark.
The tripod worked great, no regrets there. The problems started when I had to mount my camera on the brand-new quick release. After one or two quick shots with automatic exposure, I wanted to get down to business and tune the exposure manually. The only lens I had with me was the kit zoom lens (Pentax-DA 1:3.5-5.6 18-55mm AL) that came with the camera. Unlike my old lenses, this one does not have an aperture ring and the aperture is adjusted with a dial on the back of the camera. I got used to this method because I shoot in aperture priority mode all the time. This time, however, nothing happened - the aperture was fixed wide open!? After a dozen shots, and much walking back and forth between my tripod and a nearby street light to decipher the camera’s LCD display (note to myself: pack a flashlight), I gave up and went home.
The solution to the problem turned out to be quite simple. Most automatisms of the modern Pentax lenses depend on a few electrical contacts between the lens and the camera body. The contacts tell the camera some information about the lens, for instance what the available range of aperture settings is and the focal lens. Apparently, one of the little pins on the lens mount had a bad contact - removing the lens from the body, wiping the contact pins, and putting the lens back on got everything working again. If only I would have gotten that idea outside!