I bought this lens along with My Nikon F60 camera body. Since day one it has been superb, the optics are crystal clear, the lens zoom range is enough for most photographs. Starting at 28mm for wide angle shots, the zoom will go all the way to 200mm, which gives you a fairly impressive range. When you consider that 50mm is reckoned to be the approximate range of vision that the human eye sees at, this gives you an indication of how much either way it can go. The lens operates at between f3.5-22 though when used on a Nikon auto focus body it should be set to the f22 setting so as to allow control via the camera. The minimum focusing distance is actually 1.75 (0.5m). In use, this gets you pretty close to the subject whilst on the 28mm setting. I found that, in order to take good close up photographs, you can either position yourself quite close to the subject and use the ?macro? setting, or move further away and use the zoom. Why might you do this, I hear you ask? Well, for a start, to alter your effective depth of field (the distance that the camera will actually see in focus). I found that using the zoom and moving back from the subject allowed me to decrease the depth of field and isolating the subject more effectively. I would like to pass comment on the manual focus aspect of this lens but have to be entirely honest and say that I have not even used it. The lens is so spot on with auto focus that I have not yet felt the need to employ it, but it is there if I ever need it. The lens is an aspherical lens. I have this following quote from the company?s website for an explanation. "Lens elements that are not spherical can reduce the total number of elements required in a lens design. They can deliver better performance while reducing weight and size. Aspherical lenses maximize optical performance while minimizing lens size and weight. Aspherical lenses help reduce some of the problems usually associated with wide angles and zooms, such as lens
flare and edge distortion. They also help deliver higher quality telephoto images." It is also from the IF range and, again, I include a quote from the website to explain this "For our telephoto and telemacro lenses, Sigma developed an internal focusing system that moves lens groups inside the lens barrel, significantly improving macro capabilities. For super wide-angle lenses with large front diameters, we created a rear focusing system that moves only the rear lens group." The lens itself is rather heavy. You can, of course, take this two ways, it is either a little too heavy or it is merely very well built. The action of the lens when auto-focusing is very good, it is not too noisy and does not seem to hunt very much before finding the right focus. All in all, an excellent lens, at an affordable price that gives an excellent range of flexibility.