Kiron also made a 28/2.8. I must have mentioned this in another posting - years ago I bought a Konica Autoreflex with a Vivitar 55/2.8 Macro which wouldn't come off. I really just wanted the lens. I took the camera to Kiplings Photo Fix, which was in the Olden Camera building. I paid them for the surgery by giving them the camera body. I still have the lens. Many years later I bought a Minolta 600si with the Minolta 50/2.8 Macro, which wouldn't come off. I disassembled the 600si (I had a number of working ones already), threw away the camera parts and kept the lens.