This is a Kenko infrared photography filter. It allows for unique photography using the infrared spectrum, which is invisible to the naked eye. Specifically, when photographing "green" in monochrome, it appears black, but with this filter, "green" appears white. However, infrared light cannot be captured without long exposure photography. Please consider that it is difficult to photograph moving subjects. Unofficially, there are modifications that extend a camera's visible light range to include infrared. With a camera that has undergone this modification, you can take many interesting photos with this filter.