1. Processing:
very good. It makes a very solid impression. The lens hood is already included and can be set up without finger acrobatics and force to the lens. In addition, the lens has a metal bayonet coupling.
2. functions:
very good. When Sigma Image Stabilization and AF can be turned off. There is also a Zoomverriegler so that the lens is not gravity forward can zoom out. However, the Sigma is so well made that you can keep the lens upside down without the zoom moves out (maybe changes the longer period of use)
3. noise of the AFS and the anti-roll bars
The AF of the Sigma is fairly quiet. Only if the object is already in focus and you press the shutter button again, the Sigma rattles audibly.
The Sigma has a stabilizer which is clearly audible when the camera is for example in a quiet room during data transmission in addition to the computer. The stabilizer is active even if you do not use it. The noise of nature outside, however, drowned out the noise, so it does not bother me. There are several postings in forums, which was a take it significantly, while others do not hear the sounds of the stabilizers of the new Sigma-generation. Available but it is definitely, the Sigma has even confirmed itself; the noise is part of a new generation of anti-roll bars that are sure to work better.
4. Quality of the stabilizers
In 125cc focal length you always get a shake-free image up T 1/80 out sometimes 3 f low at 1/60 when you concentrate and keep the hand steady. At 18mm can easily be stable images at T 1/10 shooting.
5. Picture Quality
In a photo Color Test ([...]), the Sigma performs very well.
In wide angle Sigma scans well, some models (I have two tested) but have a tendency to have a sharpness drop at wide angle in one of the four corners, but in a small degree, the one perceives only in full-screen view. When comparing the performance with a Canon 18-200 IS, so are the wide angle worlds between the two lenses in favor of Sigma. Even at full aperture, the Sigma thins at 18mm still well and has no zoom on for soup typical extreme sharpness waste to the edges. A small drawback is the chromatic aberration at wide angle and at the long end, but they are also weaker than that of Canon 18-200 mm and in about the wide angle end with those of Canon 25-105er L are comparable at 24mm. Only the Canon KIT delivers thinner fringing. The Bilqualität incidentally compare with 18mm roughly with the Canon 18-55mm IS KIT.
The strength of the sigmoid colon is at the telephoto 40-125 mm. Especially at the long end (90-125mm) it delivers tack-sharp images that do not need to hide from an L lens. At maximum aperture at 125mm but it tends to vignetting and in low light conditions can also be found here fringing.
In the area between 50-85mm, it can be very well used as a portrait lens, also here the focus is more than satisfactory, but of course can not keep up with the typical portrait-prime lenses (Canon 50 / 1.2 Canon or '85).
Conclusion: So far I could for my 1,6er crop camera (EOS 1000D) found no "Always plan / holiday lens", which is so well crafted and delivered in all focal lengths longer than ordinary (18mm) to very good (125mm) images, while such a large focal range covering and an image stabilizer has. The price / performance ratio is, if you caught a good Sigma (see final comment) unbeatable.
What I miss, however, is the Macro function so I could do without on holiday on my 100mm Macro.
Finally it should be noted that there seems to be a great series variance in this sigma. In various forums to extreme praise alternates with complaints about Fehlfokusse from (especially front focus). I have tested two sigmoid colon and actually that was a pretty dull in the range 125mm, the other had a slightly stronger sharpness drop to the lower left corner (this I have kept).
