Lens autofocus systems can come in many forms, from basic screw-drive, through ultrasonic motors, stepping motors, and more recently, voice coil motors (VCM). What is VCM? To quote Canon, linear VCM autofocus:
"....uses magnetic force for fast, fluid-focusing adjustments. The focus unit is attached to a coil of wire which is positioned between drive magnets. These drive magnets shift back and forth to adjust the position of the magnetic field, which in turn moves the coil and the focus unit linearly in the lens barrel."
This design is great for autofocus speed, precision and quietness, plus it's better-able to move large, heavy focus lens groups, just as you'd find in fast prime lenses. 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.
You'd be forgiven for thinking that VCM autofocus is a Canon invention, but the technology is older and more widespread than that. When you factor the numerous advantages of VCM AF, it was only a matter of time before a third-party lens manufacturer developed its own interpretation. And according to the Canon Rumors, that manufacturer is Chinese lens manufacturer, Yongnuo.
The tech is said to be making its way into the brand's upcoming Sony E-mount lenses, and potentially also its Canon-fit offerings. Logically that would seems to suggest RF-mount lenses, but maybe there could also be scope for Yongnuo to equip one or more of its EF-mount optics with VCM AF?
It's perhaps surprising that a more established brand like Sigma or Tamron hasn't been the first third-party lens manufacturer to develop a VCM AF system. 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. But in the last few years we've seen the likes of Laowa, Viltrox, TTArtisan, 7Artisans all developing their own autofocus lenses, so it was only a matter of time before a Chinese lens manufacturer joined the exclusive VCM club.
No doubt some may be surprised that Chinese lenses could be as advanced as those from Japan or Germany. But considering China is the manufacturing center of the world, capable of producing the latest iPhones and electric cars, then why shouldn't this global superpower be able to manufacture another precision object like a VCM autofocus lens?
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