This is nut! I thought the FE 28mm would be the smallest AF lens on any a7xxx series. Well, I was wrong. I bought this Canon EF 40mm f2.8 STM in July 2012 when it was just released and have not used since I sold my 50D almost 3yrs ago. It wouldn't worth much to resale, a good lens, compact and small so that is the only Canon lens that I've been keeping...until now. Comparison Sample @ f2.8 and it works great. No! I didn't buy the MC-11 for the sole purpose of using it for the Canon 40mm STM. It's for this...and maybe more to come in the future. Sony OEM lenses have been going big, heavy and expensive...so why the heck not?