It seems to me that the construction of lenses needs to be updated in order to accommodate this zoom. It was explained to us that there is no lighter zoom than 2.8, but it turned out that lenses also contain "firmware." Sigma did a terrific job. A product of of high quality, distinguishable by its substantially increased weight and the presence of 24-105 and 70-200 LIS lenses in sizes that are rather modest (how much glass did they pack into it?). According to the illustration, there are no concessions made beginning at 1.8. Sharp, with very little blurring or other distortions. You are now able to achieve on the "crop" what was before impossible with any zooms thanks to aperture 1.8. The color rendering is slightly warmer in comparison to the "original" optics, but the difference is so "slight" that it is unclear which brand's color is more accurate: "Sigma" yellow or "Canon" blue? The autofocus mechanism is completely silent but produces an odd tapping sound. Autofocus continues to be a sore spot for Sigma's otherwise impressive lineup of products. I didn't expect that there would be any issues with focus at a wide angle, where it goes sharply "from the belly" to "infinity," but with such aperture, the depth of field is centimeters, and when the aperture is covered, the meaning in this lens evaporates. It is not about front-back focus, which can be solved by correction in the camera, or even better, by using the Sigma docking station. Sigma autofocus does not provide accuracy in phase focusing, and the issue is not about front-back focus (another technological breakthrough). Even though I was looking through the viewfinder of the 7D, I still have my doubts about whether or not I captured a clear image with the camera that was set on a tripod. On the bayonet contacts found on my copy, there were not even the tiniest scuffs or scratches. They don't even make an attempt to align the lenses before they leave the factory? Despite this, I came to the conclusion that I would not be returning the lens to the store. In the first place, the Samyangs, Zeiss, and the new Sigma with the Zeiss are all trying to compare, and there is no autofocus by definition; in the second place, the focus hit is one hundred percent when using Live View. I have 7D, but the people who have 70D will be even more impressive. Lastly, I have high hopes that Sigma will be able to enhance their phase autofocus after the introduction of their new firmware. And most significantly, no other manufacturer offers optics like this one does.
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