Just published the CHSOS Infrared Photography Lenses Database. Anybody is welcomed to ship their lenses to be tested for infrared photography and be added to the database. Also everybody with a Nikon DSLR camera modified for Infrared is welcomed to contribute to this database by doing a similar test and providing the photos to be posted here.
Lenses show hotspots when shooting infrared photography. Hotspots are caused by the coatings inside the lens barrel and the lens elements or by the interaction between the lens elements and the imaging sensor. Hotspots become more apparent at higher aperture numbers, while often disappear at the lowest numbers. Depending on the application and the task the infrared photo should be taken, low or high aperture numbers could be necessary. For the specific needs of infrared photography for art documentation it is useful to have detailed information on lenses behavior at different aperture numbers. This database tests only Nikon lenses.