- Ultrasonic Motor (USM)
This motor is fast, accurate, and nearly silent, and is often used in high-end lenses. It uses ultrasonic vibrations to drive the focusing elements. There are two types of USM motors: Ring type USM, which is larger and faster, and Micro USM, which is smaller and lighter. - Nano USM
This is an updated version of the USM motor that's very small but still delivers high autofocus performance. It's designed to provide the speed needed for stills while also offering smooth, steady adjustment for video. - Stepping Motor (STM)
This motor is operated by pulse electricity, which allows for a quick response time and high level of controllability. It's also structurally simple, which promotes smooth and silent operation
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