UV filters are generally not incorporated into lenses. Typically you have to use a screw-on filter for this, and this is only needed for film photography. On

UV filters are generally not incorporated into lenses. Typically you have to use a screw-on filter for this, and this is only needed for film photography. On digital sensors, the sensor contains the filter, usually some sort of Bayer filter that also blocks UV. The fluorite lens elements that Canon uses are desirable not just for their low refractive index, but also precisely because they are highly transparent in the IR and UV range. The 400mm used in this particular array uses two fluorite elements, and is one the main reasons it's suitable for this application.