I have not tested it with comparable ultra zoom, but compared with the following lenses: the Canon 28-135 zoom 1: 3.5-5.6 IS and 70-300 1: 4-5.6 IS, as well as the SIGMA wide angle zoom 17-35 1: 2.8-4 EX.
Finally, I wanted to save the constant Wechslerei just these 3 lenses without significant loss of quality to me.
After several days of intensive tests on brick masonry, at tables that I've littered with small parts, with well and poorly lit close-ups and distant subjects such as street signs at dusk I come to a clear conclusion: This lens is a real feat in this area!
Only downside: are illuminated poor photos in both the wide-angle, and at the telephoto end. This but in such small extent (in the age of digital imaging eh easy to correct) that this is the lesser evil seems to me personally as opposed to no longer accruing Objetivwechseln to be. At night a Sativ eh duty of demher it bothers then even if the shutter speed is a little longer.
The Stabilizer seems to be a bit better at Canon, but as with night scenes, it is advisable to provide also for telephoto shots to stand to grab the camera or in the alternative, hang up somewhere. Nevertheless, even in this objective a not thinking off aids.
In daylight there is in this purely objective nothing to complain about. When the maximum or lowest 18-250 focal lengths of Canon opposes the middle focal lengths of SIGMA zooms, the SIGMA cuts in some cases even better.
Autofocus is fast and works well in the dark and at the telephoto end properly.
Very practical is the Lock function that prevents the lens extends automatically when it hangs down. With older lenses that comes like before times.
I can not tell you how the SIGMA compared to Tamron's world record Zoom (18-270) or similar lenses (eg Canon 18-200) behaves. But I can say that there is a real and serious alternative to the previously used by me zoom that indeed each apply to in the art as excellent lenses.
Basically, of course, is true: it is about to see an "slacker-lens" and its should be aware of. Comparisons with fixed focal lengths considers it of course was not. It is intended to facilitate a walks and excursions, enabling quick, responsive shooting without annoying changing lenses and provide the photographer still satisfied.
This objective satisfies the SIGMA 18-250mm 1: 3.5-6.3 DC OS HSM. Filter Size M72