deserved 6 stars

This is the small, lightweight, handy and highly recommended alternative to high-aperture (and more expensive) 2,8er zoom Canon (or alternatively by Tamron). I'll take him with love when I flexibility to telephoto in want without having an overly heavy equipment here. In addition, this push among the most reliable precision workers in my lens collection. It shows in practice no weaknesses (and here writes a fixed focal length Freak!): Already at full aperture very sharp at all focal lengths, Fade brings just a tad bit more sharpness. Color fringing (chromatic aberration) and vignetting are virtually a non-issue, at least not at cameras with smaller APS-C sensor as my EOS 50D / 450D. The zoom brings beautiful vibrant colors, the 8-blade iris produces a picturesque harmonious bokeh (background blur). He is just a real L lens.

Other pluses are the enormously fast ultrasound focus that is very reliable precise about the extremely fast, but not always uncritical 50D (50D only enable the central autofocus area when it comes to action!). The optical image stabilization of the newer generation is efficiently on enormous: according to Canon takes you up to four (!!) stops - definitely are in practice non-moving objects amazingly long exposure times from hand in it. If lightning is allowed, the zoom can be had pretty well used indoors - it must then be no 2,8er.

Super is also the small close range of just 1.2 m, which already offers good potential macro with a maximum of 0.21 times the image magnification and the zoom thus making it a versatile all-rounder.

Operation is pure pleasure: the mechanism is very precise and smooth (the zoom ring almost too easy), the ultrasonic drive allows full manual intervention at any time, feel and finish are perfect. Only the black, plastic-like rather Streulichtblende falls visually somewhat. Four switches have the following functions: switching close range from a close range of 1.2 m to a remote area from 3 m for the optimum Auto Focus (AF) mode, turning the AF, turn off the anti-roll bars, switching the stabilizers between a normal mode and a for fast Mitzieher (Sport, past flying birds).

The only complaint: Apparently Canon calculated the price so low that no tripod mount included here is also likely the supplied bag in suede appearance the lens hardly protect. In other L lenses Canon is more generous. As Stativschelle I recommend the cheap and good alternative of Delamax metal tripod mount for Canon EF 70-200 f4 L (IS) USM, 300mm f4 L USM, 400 f5.6 L USM lenses with Mount Ring A (W) - white, because the original Canon-collar costs fourfold.

Strengths:
+ Amazingly light, compact and easy to handle
+ Ideal for petite woman hands, still not too small for men hands
+ Very sharp even at the beginning of Aperture
+ In practice no striking optical zoom weaknesses as typical sharpness dips at certain focal lengths, distortion, vignetting or chromatic aberrations (at least on APS cameras)
+ Faster, more precise and silent ultrasonic autofocus
+ Super stability, bringing to 4 stops
+ Initial aperture of 4 is sufficient for many situations
+ Beautiful bokeh thanks to 8-blade iris
+ Operation of zoom and manual focus ring easily, accurately and sensitively
+ Processing L-professional class, ideal for harsh environments
+ Weatherproof
+ Real value system for long use
+ Great value for money.

Weaknesses (laboriously scraped together):
- Initial aperture 4 is not just the beginning of Aperture 2.8
- Supplied lens hood would look in white instead of black (outside) of noble
- 67 mm filter diameter a little exotic, you probably have to einrechnen buying new filters
- No tripod mount included, unsuitable pack bag.

Conclusion: great alternative to the larger, heavier and more expensive 2,8er zoom in the 70-200 mm class. Thoroughly recommended for those who can live with the reduced light intensity. I would give this push even 6 star, if that were possible.