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Message: <blockquote data-quote="RJM" data-source="post: 1676169" data-attributes="member: 66340">I use the Sigma 150-500mm. It is a nice lens and quite sharp through most of the range, especially at F8 on a DX camera. The MTF curves for the lens show this to be true so any "softness" you see in posted pics is more likely due to operator error or using a FX body. Mechanically it is kinda "noisy" to the shooter but silent to those standing next to you. Handheld shots can be very nice depending on distance of course. It will sometime hunt for focus at telephoto (a limiter would have been nice) but you can grab the focus ring at any time to manually correct.  You can also use it with a cellotape modified Sigma 1.4TC and still get Auto Focus but focus can be erratic and the lens will tend to overexpose by a full stop. Using the TC unmodified requires Manual focus (watch the focus indicator light in the viewfinder) but can produce more consistent results in sketchy light.  I have a thread somewhere here in the last year on using it with the D90 if you search. cheers,Rick</blockquote>