Originally posted by Ash Yes mate. On the new copy I evaluated from B&H, the 70-200 HSM just hunted in an oscillatory manner without being able to lock on focus whilst having the TC on it. Without the TC of course it was fine. But to me it defeats the purpose of having an SDM/HSM capable TC if it's not able to extend the long end of a lens reliably.
Good to know, thanks. 95% of my pics with my 70-200 are with a 1.4x, but the other 5% I have to have f2.8, so I'll stick with my non-HSM version for now. Surely Sigma realise (and Pentax for that matter) that this is a killer for their HSM model as so many wnat the flexibility to be able to use a TC.