This article provides a comprehensive overview of Canon's autofocus (AF) motor technologies used in their EF and RF lenses. It details the evolution from the original Arc Form Drive (AFD) to the more advanced UltraSonic Motors (USM) – ring-type, micro-USM, and nano-USM – and the Stepping Motor (STM). Each motor type is described in terms of its operating principles, performance characteristics (speed, noise, accuracy), and typical applications. The article highlights the advantages of USM for speed and quiet operation, particularly the ring-type USM for professional lenses, and the benefits of STM for smooth and silent focusing during video recording. It also covers the power-saving Lead-screw type STM found in some smaller lenses. Essentially, the article serves as a technical reference for understanding the different AF motor technologies employed by Canon and how they relate to lens performance.
This comprehensive article meticulously dissects the evolution and intricacies of Canon's autofocus (AF) motor technology employed in both their EF and RF lens systems. It begins by establishing the fundamental principles of autofocus, explaining how the lens adjusts its elements to achieve precise focus on a subject. The article then delves into a detailed historical overview of Canon's AF motor progression, starting with the original Arc Form Drive (AFD) motor, which, while innovative for its time, suffered from limitations in speed and noise.
The narrative then transitions to the more advanced and widely adopted ring-type Ultrasonic Motor (USM), highlighting its superior performance characteristics, such as swift and near-silent operation. The author meticulously categorizes the different types of USM implementations, distinguishing between the ring-type USM, micro-USM, and the nano-USM, explaining the subtle yet significant differences in their construction, performance, and application within various lens models. The advantages of USM, including full-time manual focus override, are also thoroughly explored.
Further expanding its scope, the article encompasses the Stepping Motor (STM) technology, emphasizing its smooth and silent operation, making it particularly suitable for video recording where operational noise is a critical concern. The evolution of STM, from the initial lead-screw type to the more refined gear-type STM, is also discussed, showcasing Canon's continuous refinement of its autofocus technology.
The author then shifts focus to the realm of RF lenses, specifically designed for Canon's mirrorless camera system. The article meticulously describes the advantages conferred by the shorter flange distance and wider throat diameter of the RF mount, enabling enhanced communication between the lens and camera body, thereby facilitating faster and more accurate autofocus performance. The integration of Nano USM in certain RF lenses is highlighted, demonstrating its ability to combine the speed of ring-type USM with the smooth, silent operation of STM.
The article concludes with a detailed table comprehensively listing a vast array of Canon EF and RF lenses, meticulously categorizing them by their respective autofocus motor types. This table serves as an invaluable reference for photographers seeking to understand the specific autofocus capabilities of different Canon lenses, aiding them in making informed decisions based on their individual photographic needs and preferences. The article, therefore, provides a thorough and exhaustive exploration of Canon's autofocus technology, tracing its development from the early days of AFD to the cutting-edge advancements in Nano USM and the specialized features of RF lenses.
Summary of Comments ( 53 )
https://news.ycombinator.com/item?id=43320230
HN users generally found the article informative, especially regarding the different autofocus motor technologies Canon uses. Several commenters shared their own experiences with specific lenses and motor types, highlighting the performance differences between USM, STM, and Nano USM. Some discussed the tradeoffs between speed, noise, and cost associated with each motor type. The practicality of micro-adjustments for autofocus was also debated, with some users finding it essential and others considering it a workaround for poor lens design. Finally, there was some discussion around the article's focus on Canon, with some users wishing for similar breakdowns of autofocus systems from other manufacturers like Nikon and Sony.
The Hacker News post titled "Canon EF and RF Lenses – All Autofocus Motors" links to an article detailing the various autofocus motor technologies Canon has used in its EF and RF lens mounts. The discussion in the comments section is relatively brief, with only a few comments focusing on specific technical details rather than broad opinions about the article itself.
One commenter points out a perceived error in the article, stating that the article incorrectly claims the STM motor is based on a piezo effect. They clarify that STM motors are actually based on a stepping motor, offering a more accurate description of its functionality. This commenter also highlights the quietness of STM motors, a characteristic particularly beneficial for video recording.
Another comment adds to this correction, emphasizing that while some focusing systems do use piezo elements, Canon's STM does not. This comment further explains that Canon's STM employs an ultrasonic motor driving a lead screw to achieve focus, contrasting it with ring-type USM systems which directly move the focusing lens group. This commenter provides more context by discussing ring USM, micro USM, and nano USM, explaining that although they differ in their implementation (direct drive vs. geared), they are all based on ultrasonic vibration principles.
A subsequent comment shifts the focus slightly, mentioning issues with the Canon EOS R's electronic viewfinder (EVF) "blackout" during continuous autofocus. This blackout refers to the momentary loss of the live view image in the EVF when the camera takes a shot. This commenter expresses frustration with the duration of the blackout, claiming it makes tracking moving subjects difficult. While related to autofocus, this comment doesn't directly address the article's content on autofocus motors themselves but rather a practical consequence of the camera system's performance.
Finally, one commenter simply expresses appreciation for the article, finding it "useful" and "interesting." This, however, doesn't provide much detail or insight into specific aspects of the discussion.
In summary, the comment section is small but offers some valuable technical clarifications regarding the article's description of STM motor technology. It also touches upon practical user experience with Canon's mirrorless autofocus system. While the discussion doesn't offer extensive debate or diverse viewpoints, it does provide helpful additions and corrections to the original article's information, especially for those interested in the nuances of Canon's autofocus technology.