My Viltrox JY-35F arrived last night. I tried my 14-54 MK1 lens first . AF is about the same speed as the m14-42 MK1 kit lens. Not really that bad, approx 1 second to AF. Good enough for land scapes and portraits. IQ. A nice improvment Next the 40-150 and 70-300 IMO , any one who has Oly 4/3 Glass and a pen camera A JY-35F adapter is good choice.