Types of Lens Autofocus Motor
1. Micro Motor
This motor is known as the most basic and economical autofocus motor. It consists of a small electrical motor that moves the lens elements to achieve focus. Micro motors are very compact and lightweight, which is suitable for constructing smaller lenses. It also usually focuses slower and noisier compared to the other autofocus motor types compared to more advanced motor types. As this motor is economical and cost-efficient, it is commonly found in cheaper and entry level lenses.
Example of lenses that use micro autofocus motors:
2. DC Motor
This motor is an improvement over the micro motors. They provide a more pleasant, faster and quieter autofocus experience. DC motor works by using the direct current power source to drive the lens elements for focusing. While the DC motors may be considered an upgrade over the basic micro motors in terms of focusing speed, they are still relatively affordable and may not provide the most precise autofocus. Hence, they are usually found in mid-range lenses.
Example of lenses that use DC autofocus motors:
- Fujinon XF 56mm f/1.2
- Fujinon XF 23mm f/1.4
- DA 18-135mm f/3.5-5.6 ED AL [IF] DC WR
- HD DA 16-85mm f/3.5-5.6 ED DC WR
- Sigma 70-300mm f/4-5.6 OS HSM
3. Ultrasonic Motor (USM)
This is the motor that is commonly used among the higher-end lenses, as the cost is higher compared to micro and DC motors, especially those produced by Canon. This USM autofocus motor is known for their fast, accurate, and nearly silent autofocus operation, making it desirable for sports, wildlife, and fast action photography. This technology uses ultrasonic vibrations to drive the focusing elements. There are two main types of USM motors, the Ring type USM and Micro USM. Ring type USM motors are larger and faster, which makes it suitable for larger telephoto lenses, while Micro USM motors are smaller and lighter, making it suitable for compact lenses.
Example of lenses that use ultrasonic autofocus motors:
- Canon EF 70-200mm f/2.8L IS III USM
- Canon EF 85mm f/1.4L IS USM
- D FA 24-70mm HD f/2.8 ED SDM WR (uses Tamron USD)
- Sigma 35mm f/1.4 DG HSM Art
4. Silent Wave Motor (SWM)
Silent Wave Motor is basically Nikon’s equivalent of Canon’s Ultrasonic Motor. It also offers fast, silent, smooth, and precise autofocus experience, which is well suited for various photography genres, including wildlife and portraiture. The SWM motor uses electromagnetic waves to drive the focusing elements. Like the USM, SWM is also available in two types of motors, the AF-S (Single Motor) and AF-P (Pulse Motor). Each comes with its own characteristics that can be optimized for specific lenses and purposes.
Example of lenses that use silent wave autofocus motors:
5. Linear Motor
Linear motors are commonly used in lenses made for mirrorless cameras. This autofocus motor provides quick and quiet autofocus performance which is suitable for video recording. The linear motor works by using electromagnetic fields to move the focusing elements along a straight path, as stated in the name. It has the capability to offer high-speed focusing and precise control, which contributes to improved tracking and subject detection used in continuous autofocus modes.
Example of lenses that use linear autofocus motors:
- Sony FE 50mm f/1.2 GM
- Sony FE 24mm f/1.4 GM
- Sony FE 400mm f/2.8 GM OSS
- Fujinon XF 33mm f/1.4
6. Stepping Motor (STM)
Stepping motors are also frequently found in mirrorless lenses, particularly those designed for video shooting and smooth focus transitions. STM technology offers silent, precise, gradual adjustments of focus and minimal abrupt changes during autofocus. As a result, it is often slower than other motor types in certain scenarios. STM motors are suitable to be used for video recording with continuous autofocus.
Example of lenses that use stepping autofocus motors:
Consideration When Buying or Selecting the Right Lens
1. Performance Factors
When selecting the right lens, photographers should take into consideration the level of autofocus performance that is needed. From there, they will be able to select a lens with a specific autofocus drive. These factors include autofocus speed, accuracy, noise level, compatibility, and reliability.
2. Compatibility and Future-Proofing
Having learned about the different types of autofocus motors, we know that some lenses are made and designed for newer mirrorless technology. So, for photographers who wish to migrate into mirrorless systems and future-proofing their equipment, they may want to consider lenses that are made with modern autofocusing motors.
3. User Experience
Different autofocus motors will provide photographers with different user experiences. Some lenses provide a pleasant user experience by providing a fast, silent, accurate, and precise autofocus, while some are just the total opposite. These experiences should be considered before purchasing a lens to ensure that the purchase is suitable for photographer’s usage.
The type of autofocus motor can impact the price of the lens. Advanced autofocus motors such as Ultrasonic Motor and Linear Motor that cost more are often found in higher-end lenses and may come with a higher price tag. This is where the photographer’s budget comes into play in determining the right lens to get while weighing the autofocus performance and their photography requirement.
5. Lens Type and Purpose
Different types of lenses are designed for different types of purposes. Genres such as portraits, landscapes, sports, macro, or general-purpose photography will have a different level of hardware requirement. Therefore, before purchasing the lens, the photographer should consider the specific requirements of your photography style and choose a lens that matches your needs. For example, fast-moving subjects may require a lens with a faster and more responsive autofocus system and vice versa.
In conclusion, selecting the appropriate autofocus drive for a lens requires careful consideration of various factors. While the advantages and disadvantages of different autofocus motor types provide a helpful starting point, it's important to recognize that performance can vary within each category due to lens design, firmware optimization, and other variables. The guidance provided in this article serves as a valuable resource for photographers, offering considerations such as budget, intended usage, system compatibility, and the desired balance between speed, noise, and reliability. By taking into account these factors and conducting thorough research, photographers can make well-informed decisions when purchasing lenses that align with their specific needs and preferences.