I have been a few years now owner of this objective and have now even read through the reviews of some users. Most data buyers of Sigma 150-500 are very satisfied. I am, too. I photograph for 40 years in the wild mainly birds and wild plants. The Sigma comes with me very frequently used I place Value at the Bird Photography on good sharpness. The Sigma makes it here for nothing. At 500 mm, the images are slightly soft. That's when a Nikon 200-400 for 6,000 .-- Euro no different. By the way I did with a friend who has the Nikon 200-400 test shots, not like many other photographers who have given their judgment here, just that easily in the open landscape, but on a stand on a so-called Siemens star. With the same aperture, distance and cut. It was found that the Nikon 200-400 is a tiny sharper than my Sigma 150-500. Only at 100 times magnification with Capture NX can be the seen. If you do not the two images side by side looks - not at all. The longest focal length of 500 mm I avoid when it comes and use about 450 mm, for I can this little yet herausvergrößern during processing. With a Nikon 200-400 the longest focal length of 400 mm is also not sharp edges. If some buyers hinbekommen no sharp photos with their Sigma 150-500, then they might have acquired a "outliers" - that is to give it, or they have done something wrong. The other day told me a photographer following: There are people who can use a kitchen knife just peel potatoes and other carve a flute so .... To get crisp landscapes come some factors. It is not possible, for example, when the air is not adequately pure, or in strong sunlight, just at lunchtime. All this is exacerbated by the zoom effect. That's just in a 10,000- euro lens. The Sigma 150-500 lens is ideally suited for aerial shots. The OS stabilizer is switched on aerial photographs from the best. But you have to try for yourself. I have often stood next to nature photographers, who wanted to make a 500 or 600 mm fixed focal length lens Flugaufnahemen. Slow-flying birds (egrets) works with exercise quite well. Birds in flight which are very mobile (Lapwing) to catch with a fixed focal length needs a lot of exercise. especially when the "flying object" is in the vicinity. Many photographers were given the object only not in the picture, while I had with my Sigma and buttstock a whole series thanks to a variable focal length, added. Under bright sunshine makes the autofocus itself sharply with a 1.4 Converter. Usually I take pictures so however only from the tripod. For aerial photographs the Converter is unsuitable. With the Converter, the images are slightly soft when photographing from a tripod, for example at the winter feeding. Certainly prime lenses are the zoom somewhat superior when it comes to sharpness. Therefore, this can not be compared, although this is done repeatedly. What I did not like about my Sigma, is the paint. Although I always transporting it with a wrapping cloth, the color has replaced in some places. The color of the lens is roughened by novelty fro something and does not adhere correctly and therefore can not keep clean, once you have touched about a green branch. In Sigma you probably noticed, because the newer lenses are outside "smooth", why not make it like that. ??? All in all I do with the Sigma in the raised hide, images of "Crisp Focus". Who does not believe, can come and see me: Google, then typing "ipernity Luscinia", then click on top Ruprik. My home with my photos on going, then pictures and albums