What is this lens good for? Never heard of something like it before. (Sony FE 100mm F2.8 STF GM OSS)

"An aperture range of f/2.8 to f/20 is available, however the implementation of the apodization filter renders this range as T5.6 to T22."What? Why? What is the purpose of this? via /r/photography https://ift.tt/2OEXDAA