Original post by: Technician X ,
This appears to be a defective infrared cutoff filter, and it is a defect seen on many D80, D40X and D60 Nikon image sensors . If you pull the filter and check the bottom under magnification, it almost looks like micro drops on the bottom side of the filter, like the coating didn't stick or is now coming off. It appears to be some sort of manufacturing defect - possibly contamination during the coating process on the bottom layer of the filter. Unfortunately there is nothing that can be done for this other than replacing the image sensor, unless you want to convert your body to infrared. Nikon never sold the cutoff filter separately, and now that Nikon has stopped selling parts you can't even get the complete image sensor. As usual, Nikon has never acknowledged the problem . . .