Powerful zoom, but not always plan for every situation

Addendum: Meanwhile, I've tested the lens also extensively on my EOS 7D. Unfortunately, the high-resolution 18-megapixel sensor of my below-noted critical fringing are even more an issue. Once z. B. photographing building against a bright sky, you can see it clearly at the edges. Sure, the 7D with its madness resolution also mercilessly, but if you want a photo of pulling, you can see precisely such mistakes. Canon ity well to follow Nikon and the JPEGs produced in the same camera chromatic aberration (color fringing =) herauszurechnen (physics allows for this type of optical errors). Nikon makes the already in his DSLR (secretly, so that no one thinks that Nikkor lenses were badly made). Alternatively Canon installing an automatic for the correction of chromatic aberrations in the DPP software. At the moment you have to unfortunately make in DPP still laboriously by hand, and in this objective, it is unfortunately necessary from time to time. Too bad, because with such elegant software correction of optical weakness would be a tip Zoom.

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Old review:
This high-intensity image I have thoroughly tested thoroughly with many photos and a measuring arrangement with Siemens star. He has impressive strengths, but also pronounced weaknesses. Given the high price the acquisition will therefore be carefully considered. Ideal is the push for "Available Light" fans who (like me) like to take pictures in low light without flash. Especially with the EOS 50D are wonderful results possible. With open aperture can be due to the shallow depth of field and blurred background objects beautiful picturesque before working out (beautiful 'bokeh') - for example, portrait or landscape architecture before. Standard lenses with smaller aperture does not allow this photographic painting. The thick But in bright light come on contours with sharp contrast fringing on (for details see minuses.). That's why the push is definitely not "Always top" for truly all cases (eg. B. midday architecture Photos in the south).

Plus points:
- Light giant, which allows continuous aperture 2.8 at all zoom levels (something special!): In little moving objects sharp images even in dim light even without too much noise possible.
- The super image stabilization brings there again 3-4 f-stops for shots from the hand (almost a night vision device).
- Bright viewfinder image even in relatively dark.
- Cameras such as the EOS 50D activate a special, high-precision AF mode 2.8.
- Quieter ultrasonic AF works perfectly, even in low light.
- Beautiful, lifelike color reproduction (rather warm tones).
- Manual focusing is sensitive, however, getting used to the arrangement of the focus ring "before" the zoom ring.
- Feel quite dibasic.

Bad points:
- Fringing (chromatic aberration, CA) high-contrast scenes (test with Siemens star, details see footnote). When Siemens star they are clearly visible, especially on the image edges, where the cheaper kit lens 18-55mm / 3.5-5.6 (newer type II!) Edges still reflects clean. Really surprising is not that: fast lenses have large, thick lenses, the light of different wavelengths (colors) to different extents break. In order to grow the CA and other artifacts (we learn in the first semester physics). Fully offset by the combination of different refractive glasses can not be that just at a push. The image stabilization makes the challenge even more complex, so the Canon's engineers had to clear compromise. In practice, the problem is only visible in certain situations (eg. As to [...] one can image examples in Lens comparison test view). Knowing this behavior can be prevented by timely changing lenses.
- Sharpness good, dimmed quite good, but not better than the 18-55 mm / 3.5-5.6 II (test with Siemens star, however, I have a particularly good 18-55 caught). Zoom Typically it takes at the telephoto end sharply.
- Vignetting (vignetting) especially in the wide-angle visible (to EOS 50D best automatic correction switch).
- Tends to slightly dust collection behind the front lens, which produce better picture quality but not equal to deteriorate not pleased with the price. Setting up a UV filter costs loose 1 stop (which buys you a fast lens?) And does not prevent lateral penetration of dust.
- Very heavy, very beautiful Oschi (with the EOS 40 / 50D good 1.5 kg).
- The important lens hood is not included.

Conclusion: In "Standard zoom" situations you should have as a backup for bright, high-contrast lighting conditions, the (small, light) 18-55 mm or another lens case.

Footnote to the home test with Siemens star:
I have a series of tests with the 17-55, the 18-55, and even shot a high-intensity fixed focal length as the second reference. Up Siemens star well illuminated. Camera (50D with me) Align tripod when measuring distances I chose different distances of 30 cm (Stern fills image off) to 10 m (star center of the picture). Measurement with short, medium, long focal length. Recording: AF and stabilizer off, manual focus with Live View and 10x loupe magnification, off with mirror lock-up and 2-second self-timer for safety's sake blur by mirror slap.