What is the difference of ultrasonic motor, stepper motor, and electromagnetic drive? Which one of these are lens-based or screwdrive? What are the advantages of lens-based servo over screwdrive and vice versa? Are camera body normally built to have autofocus motor or normally lens-based?

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  1. Technological difference
  2. Usage difference
  3. Price and availability
  4. Advancement in recent years
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