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Canon EF 17-40mm f/4 USM L - Retest @ 15mp |
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Lens Reviews -
Canon EOS (APS-C)
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Review by Klaus Schroiff, published August 2009
Special thanks to Philipp Schürmann for providing this lens!
Introduction
The Canon EF 17-40mm f/4 USM L has already been tested on the old EOS 350D @ 8mp so this is only a retest based on the EOS 50D@ 15mp (APS-C). Therefore you may forgive us that we simply reused portions of the old article.
The Canon EF 17-40mm f/4 USM L is one of the most popular L class lenses thanks to its relatively affordable price and its dual purpose scope - it can serve as a "27-64mm" standard zoom lens on APS-C DSLRs and it's an ultra-wide zoom lens with an attractive range on full format DSLRs.
The build quality of this lens is exceptionally high just as you would expect it from a Canon L lens. No wobbling whatsoever and smooth controls - almost perfect. The lens is also designed to survive in harsh conditions with a sealing against dust and moisture. The outer length of the lens remains constant although the inner lens tube moves a little according to the zoom setting. Needless to say - the front element does not rotate during focusing or zooming operations.
The lens has a ring-type USM drive based on a front-focusing system resulting in an extremely fast AF speed. AF accuracy was also not an issue during the field tests. Typical for ring-type USM lenses full-time manual focusing is always possible in one-shot AF mode.
| Specifications |
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| Equiv. focal length | 27-64 mm (full format equivalent) |
| Equiv. aperture | f/6.4 (full format equivalent, in terms of depth-of-field) |
| Optical construction | 12 elements in 9 groups inc. 3x aspherical and 1x SUD elements |
| Number of aperture blades | 7 (circular) |
| min. focus distance | 0.28 m (max. magnification ratio ~1:4 @ 40mm) |
| Dimensions | 84 x 97 mm |
| Weight | 475 g |
| Filter size | 77 mm (non-rotating) |
| Hood | included, petal-shaped |
| Other features | gel filter slot (rear), sealing |
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