I shot some time lapse this morning and the entire 200 frame series came out seriously over exposed. It took me about 5 minutes to discover what the problem was. The aperture mechanism in my Nikon AF 24-85 mm f/2.8-4D is binding and can't reliably stop down from wide open (to AF) to the smaller than wide open aperture I wanted to use. For those that don't know: The lens aperture is moved by a motor in the camera body (all Nikon DSLR bodies). When a lens is not mounted on a Nikon DSLR the lens aperture is closed to as small as it can get by a spring. When the lens is mounted on the body, the in-the-camera to lens aperture linkage opens the aperture as wide as it can go. That's so what we see in the viewfinder through the lens is a bright as possible and so the AF system doesn't have to wait to do it's thing when the shutter is 1/2 pressed. I figure the repair will cost me about $250, which would be about $100 less than less than replacing the (bought it used) lens.