Originally Posted by
GrumpyDiver
John, the 175-500mm was discontinued quite a few years ago; I don't know exactly when, but the 150-500mm came out in 2008 and the stabilized 50-500mm came out in 2010, I think.
We picked up our copy of the 150-500mm in mid-2011, and the 175-500mm was not available. We had a look a number of long zooms as we were planning a trip to Namibia. I already owned the 80-400mm Nikkor and did not want to get two identical lenses (it uses the camera's focus motor and is not blazingly fast in focusing), so we had a very thorough look at the Sigma and Tamrons.