Lens autofocus systems can come in many forms, from basic screw-drive, through ultrasonic motors, stepping motors, and more recently, voice coil motors (VCM). This explains why all the Canon VCM lenses so far have been fast f/1.4 primes, such as the RF 85mm f/1.4 L VCM, RF 50mm f/1.4 L VCM and the RF 24mm f/1.4 L VCM. The Canon RF 50mm f/1.4 L VCM (Image credit: Future)You'd be forgiven for thinking that VCM autofocus is a Canon invention, but the technology is older and more widespread than that. After all, it wasn't that long ago that Chinese lenses were almost all manual focus, and most didn't even have any electrical contacts. The Viltrox AF 135mm F1.8 LAB: just one of many high quality Chinese lenses we've seen in recent years (Image credit: Matthew Richards)No doubt some may be surprised that Chinese lenses could be as advanced as those from Japan or Germany.