This blog allows me to disseminate knowledge I think should be readily available. If I find myself ranting, I try to make sure it's informative, and not completely subjective. I try to offer solutions--not problems--but in the case I do present a problem, please feel free to post a comment.
With reference to this earlier post, I wanted to make a comparison of a Nikon 18-200mm lens and a Sigma 150-500mm on a D90.
18-200mm
150-500mm
Wide
Telephoto
So, the widest the 150-500mm lens will go is only a little wider than the narrowest the 18-200mm lens goes.
The narrowest the 150-500mm lens goes is much narrower than the 18-200mm.