The Canon EF 200mm f/2.0 L IS USM Lens' Ring USM (Ultrasonic Motor) driven AF is extremely fast and very accurate. AI Servo tracking of in-motion subjects is definitely a strength of this lens. The internal-focusing lens does not extend and does not rotate the front element - which does not matter in regards to filter use as this lens does not accept front-mount filters (even if they could be attached, they would cost a fortune). A fixed-size lens is nicer to use than one that changes size - most fixed focal length lenses do not extend. FTM (Full Time Manual) focusing is enabled.
A 2-position focus limiter switch allows the shortest focusing distance to be limited to 11.5' (3.5m) to infinity (can reduce AF lock time in certain situations). Full range focusing is of course an option - from 6.2' (1.9m) to infinity. The Canon EF 200mm f/2.0 L IS USM Lens includes a Focus Preset feature. Set the Focus Preset to a specific distance - when your shooting needs require that specific distance, press the Focus Preset button.
Autofocus stop buttons on the black ring near the objective lens allow autofocus to be temporarily suspended. Those not used to this feature may need an example of a situation where it is useful ... I often shoot sports in AI Servo AF mode using the center AF point only. At some point, I may want to grab a portrait using the focus and recompose technique - which does not work in AI Servo mode where the camera is constantly finding the correct new focus distance. So, I focus on my subject, press one of the AF Stop buttons, recompose and take the shot. I get my portrait and am immediately ready to go back to the action.
more : the-digital-picture
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