Canon EF 17-40mm f4L USM - Manual (Page 2)

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Thank you for purchasing a Canon product.
The Canon EF17-40mm f/4L USM is a high-
performance wide-angle zoom lens.
• “USM” stands for Ultrasonic Motor.
Features
1. Two aspherical elements and a Super UD
element result in outstanding image
delineation.
2. Ultrasonic motor (USM) for quick and quiet
autofocusing.
3. Manual focusing is available after the subject
comes into focus in autofocus mode (ONE
SHOT AF).
4. A truly round aperture hole results in a nicer
background blur.
5. Tight seal structure ensures excellent dust-
proof and drip-proof performance.
• Since the front element of this lens moves when
focusing (zooming), you need to attach a Canon
PROTECT filter sold separately for adequate
dust- and water-resistant performance. Without
a filter, the lens is not dust or water-resistant.
Conventions used in this instruction
Warning to prevent lens or camera
malfunction or damage.
Supplementary notes on using the lens
and taking pictures.
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