They're generally called "superzooms", sometimes "all-in-one" or "vacation" lenses. I call them "zoo lenses" because they cover a wide enough spread of focal lengths to cover any shooting situation at the zoo, whether the critter is big and right in front of you, or small and way off in the back of its enclosure.
They typically have a 7X to 10X focal length range... wait, let me explain something.
Most people see the number followed by an "X" and assume it refers to view magnification, since that's what it signifies with telescopes and microscopes and the like. With cameras, however, it refers to the range of focal lengths.
A 35-70mm zoom lens would be a 2X zoom, going from a wide-ish viewing angle to the very shortest edge of telephoto. A 70-210mm would be a 3X, while a 24-240mm would be a 10X, et cetera.
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12-200mm on the Olympus E-M1X in the photo above, the equivalent of a 24-400mm lens on a full-frame camera, is at the extreme end of superzoom ranges. It's able to shoot from comfortably wide angles to a very credible long telephoto length suitable for urban wildlife.
One of the first really good superzooms was Nikon's 28-200mm AF-D, which was replaced by the even more compact 28-200mm f/3.5-5.6G in 2003. Now discontinued, those lenses have gotten a little cult-y due to their small size and can fetch a premium on the used market.
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Nikon D700, 28-200mm f/3.5-5.6G |
The superzoom I get the most use out of is for DX Nikons, though: the 18-200mm f/3.5-5.6 VR II. I've used it on all my crop sensor Nikon DSLR bodies and the only one on which I don't like it is the D7100, as the 24MP sensor reveals its limitations. It's plenty sharp on the older D300S, though.
Basically, any time you're going someplace where you don't want to carry several lenses and have no idea what you're going to be shooting, the Superzoom is your Swiss Army knife lens. Vacation, the zoo, just walking around the neighborhood, it's your one-lens solution.
Quality ones tend to be moderately spendy, because there's a lot of optical jiggery-pokery happening in there to keep image quality reasonably decent, and they're not so hot for indoors or low light because of their fairly slow aperture range, but they're my go-to solution for a sunny day stroll around Broad Ripple if the squirrels are out and about.