| With a constant f/2.8 aperture throughout the zoom range and a 3-stop Image Stabilizer, the EF-S 17-55mm f/2.8 IS USM provides outstanding performance and framing flexibility in low light conditions. | |
| High performance wide angle zoom Click on the Details for more info |
| EF-S17-55mm f/2.8 IS USM | ||||
| This month's Technical Report introduces the EF-S17-55mm f/2.8 IS USM large aperture, high-performance standard zoom lens specifically for the EOS DIGITAL cameras using an APS-C size digital imaging element and the EF85mm f/1.2L II USM large aperture medium telephoto L-series lens, both announced together with the EOS 30D. | ||||
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| Photo 1 EF-S17-55mm f/2.8 IS USM | ||||
Concept of development The EF-S17-55mm f/2.8 IS USM (Photo 1) is a large aperture, high-performance standard zoom lens with a maximum aperture of f/2.8. It was developed to bolster the lineup of dedicated interchangeable lenses for EOS DIGITAL cameras using APS-C size digital imaging elements (EOS 30D, EOS 20D, EOS 20Da, EOS Kiss Digital N and EOS Kiss Digital as of May 2006). The development concept is as follows: Large aperture with maximum aperture of f/2.8 High image definition throughout the entire zoom range Image stabilization equal to about three shutter speeds Digital camera compatibility Feature 1: Large aperture with maximum aperture of f/2.8 The optical system of the EF-S17-55mm f/2.8 IS USM is designed to provide a large aperture, high definition and image stabilization. The optical design takes advantage of the smaller image circle and shorter back focus of EF-S lenses optimized for APS-C size digital imaging elements, enabling a large f/2.8 maximum aperture while keeping the optical system compact. It has inner focusing by the second lens group and parallel shift-lens image stabilization by the twelfth and thirteenth lens groups (image stabilizer lens group) (Fig. 1). The focal length is equivalent to 27-88mm in full-frame 35mm format. | ||||
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| Fig. 1 EF-S17-55mm f/2.8 IS USM Optical System | ||||
Feature 2: Ultrahigh image quality The optical system of 19 elements in 12 groups uses three precision aspherical lenses of two types, which helps minimize aberrations that occur during zooming and focusing, enabling the large f/2.8 maximum aperture and high definition throughout the entire zoom range. Two UD lenses are used to minimize chromatic aberrations throughout the zoom range, providing L-series excellent quality images with both high resolution and contrast throughout the zoom and focusing ranges (Fig. 2). | ||||
Fig. 2 MTF Characteristic Charts of EF-S17-55mm f/2.8 IS USM | ||||
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| Thick lines: 10 lines/mm; thin lines: 30 lines/mm. The darker black lines represent the MTF characteristics at maximum aperture; the blue lines at f/8. The solid lines trace the radial S (sagittal) curve, while the broken lines trace the tangential M (meridional) curve. | ||||
Feature 3: Image stabilization of about three shutter speeds Through the use of a dedicated high-performance compact image stabilization (IS) unit (Photo 3), developed specifically for the EF-S17-55mm f/2.8 IS USM, and a vibration gyro for precise camera shake detection, it gives image stabilization equivalent to using a shutter speed about three steps faster (Fig. 3). | ||||
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| Photo 3 EF-S17-55mm f/2.8 IS USM IS unit | ||||
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| Fig. 3 EF-S17-55mm f/2.8 IS USM camera-shake correction | ||||
The general rule for the slowest permissable shutter speed to avoid camera shake is 1/focal length in seconds, or for the APS-C format, 1/(focal lengthx1.6) in seconds so the slowest acceptable shutter speed for 17mm focal length is about 1/30 seconds. Using the image stablizer, good images can be obtained at a rate of 90% or over even at 1/8sec. Furthermore, the f/2.8 maximum aperture allows a fast shutter speed, thus hand-held shooting is possible even in low light (Photo 4, 5). | ||||
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| (Photo 4 and 5 taken with an EOS 30D at 17mm, 1/4sec) | ||||
The image stabilizer used in the EF-S17-55mm f/2.8 IS USM also has the following excellent features. • The image stabilizer is activated within half a second after pressing the shutter button halfway, allowing the user to capture the decisive moment. • The same image stabilizer effects can be attained when using a monopod as in hand-held shooting. • There are no restrictions on using a tripod. | ||||
Feature 4: Lens coating optimized for use with digital SLR cameras The EF-S17-55mm f/2.8 IS USM optical design and coating optimized for use with digital SLR cameras gives both good color balance and minimizes ghost and flare attributable to surface reflections from the digital imaging element. Feature 5: Superb operability Closest focusing distance of 0.35 meters The 0.35 meter minimum focusing distance throughout the zoom range is achieved by increasing the power of the focusing lens group. The maximum magnification is 0.17x at 55mm (field of view: 88 x 131mm). Circular aperture for attractive bokeh effects Thanks to the EMD's (electromagnetic diaphragm) circular aperture, the lens provides attractive blur effects (bokeh). Silent, high-speed AF In addition to the silent ring-type ultrasonic motor (USM) and inner focusing, the high-speed CPU and optimized AF algorithm contribute to very fast autofocus. Manual focusing enabled even in AF mode The EF-S17-55mm f/2.8 IS USM has full-time mechanical manual focusing that allows manual focus after one-shot AF operation without leaving AF mode. Switch design that prevents unintended switching The focus mode switch and IS switch are designed to prevent unintended switching during shooting or when being carried. Non-rotating filter ring Since the filter does not rotate while zooming or focusing, circular PL (polarizing) filters are easy to use. Use of the Canon 77mm PL-CII filter is recommended to prevent vignetting. Dedicated large scalloped hood with superb light blocking The EW-83J, a large scalloped hood dedicated to the EF-S17-55mm f/2.8 IS USM, has superior antireflection flocking on the inner surface. It is very effective in keeping unwanted light out of the lens (Photo 6). | ||||
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| Photo 6 EW-83J dedicated hood for EF-S17-55mm f/2.8 IS USM | ||||
Feature 6: Environmentally friendly design The optical system contains only environmentally friendly lead-free glasses. Effective from July 2006, EU (European Union) will restrict the use of certain hazardous substances* in the electrical and electronic equipment according to the ''EU's Restrictions on Hazardous Substances (RoHS) Directive''. The EF-S17-55mm f/2.8 IS USM is already in compliance with Canon's own standard covering the RoHS directives including those still being finalized. *Six substances: lead, mercury, cadmium, hexavalent chromium, bromine flame retardant PBB (polybrominated biphenyl), and PBDE (polybrominated diphenyl ether). |
