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Nikon 18-200 VS 70-200 (F2.8)?
Is Nikon 18-200 70-200 does work?
It depends on what work you do. The 18-200 includes the extension of the image (zoom) the lens 70-200 capabilitites ago. The differences include the quality of the image (the 70-200 is a lens prosumer category, while that the consumer is strictly 18-200) and 70-200 lens is much faster, which means you can take a picture equally exposed quarter of the light that the 18-200mm can. And a 2.8 constant aperture lens will give that nice shallow depth of field open for a portrait or sports photography.
A day with nikon 18-200 vr