K. L. Turner
I purchased this lens for use as a lower-cost telephoto for bird and wildlife photography. I had heard good things about the sharpness and image stabilization of this lens, although the focus speed was not said to be fantastic. I had not had great results from Tamron lenses in the past, but the word was that they had improved dramatically and that this lens was a great deal. I figured I would give it a shot. The first lens I got, new from a reputable vendor, was simply defective. The images were very soft and there was no range in which objects were in focus; everything from close to far was blurry. I returned it to the vendor for replacement. The replacement was not as terrible as the first, but it was still soft and had weird specular highlights, for lack of a better way to describe it. The glass elements clearly caused some distortion of the light, which became even more obvious when the images were cropped. The images were "passable" for someone who never crops and never prints large, but they were nowhere near as good as I had expected. The image stabilization is really very good, at least on stationary objects, although it uses up battery life rapidly. When I switched it to the mode for following moving objects, it did not perform as well, but perhaps this is due more to the lens slow autofocus. The autofocus is noisy and sounds more like an industrial machine rather than a piece of performance equipment, and it can not keep up with moving objects. It does even worse in less-than-stellar lighting. In the end I exchanged the replacement Tamron lens for a Canon 100-400mm, and when compared side-by-side at full zoom the images from the Canon 100-400 far exceed the quality from the Tamron 150-600. Although it costs a bit more and it doesnt have as much reach, I feel that the extra reach is wasted if the images are so soft that the detail is lost. Also, the Canon lens, while still hefty, is substantially lighter, and the autofocus is much faster and quieter. It also can focus much closer, making it more useful for macro photography, and its image stabilization is excellent. Also, despite being lighter in weight, the Canon actually feels more solidly built. The image below shows a side-by-side comparison of the moon taken with the replacement Tamron (not the defective one) and the Canon lens I finally settled on. These images were taken in the exact same circumstances a few days apart (which accounts for the change in the moons phase appearance). More details are visible, and sharper, with the Canon lens, despite it maxing out at 400mm rather than 600mm.