I wonder how many are suffering with poor quality lenses without knowing it. My first digital SLR was a D80 with two lenses, A Sigma (70-300) and a Nikon (18-70). They were just Ok except that the Nikon later developed a defect that had to be serviced. I than got myself a Sigma 50mm macro lens. For the first time I very often found a picture I really liked. Because I often go to a nature park with game I was thinking of a longer lens but was reluctant to do so because very few of my pictures (if any) were stunning and I was wondering weather my technique was faulty. I upgraded my camera first to a D200 and than to a D300S. I never the less, got my self a Sigma (150-500), disaster, the photos were very close to be useless. I did a range of tests and the pictures were very poor indeed. I surrendered some of my photos to the Nikonians and one of the suggestions was that my photos were taken at a too low shutter speed. I repeated the tests, gave a report to the dealer, returned the lens and 4-weeks later I had a replacement. I still am not a good photographer but to the pictures with this lens, a Sigma (150-500) is astonishing (in my opinion). I had difficulty in selecting two pictures. Both of them are heavily cropped and as I used ISO 800 on my D300S, the pictures are a bit grainy. Suggestion: To the very able photographers amongst you, for a fee, please make your self available to help novices like me. I am sure there are many other photographers with lenses that are not up to standard. I do not think I will ever again buy a lens before I had it tested by an expert photographer.