Do Nikon teleconverters work on the Sigma 105 macro?

In a word:  no.  And not just “they’re unsupported”, or that they have optical issues – they physically will not connect.  They are deliberately keyed to be incompatible.  Nikon teleconverters have a protrusion on their lens mount, which prevents any ‘standard’ Nikon-mount lens from attaching, unless that lens is missing a particular obstruction on the rear mount.

This is not unique to the Sigma 105, by any means.  Nikon’s own 70-300, for example, has the exact same obstruction and also will not mount to any Nikon teleconverter (or at least, not any of the current models, of the 1.4x, 1.7x or 2x).

This is very disappointing, and an odd decision by Sigma – it was they, after all, who deliberately included the obstruction on the rear mount.  The teleconverters would mount just fine otherwise – there is just enough clearance to the rear element.

In contrast, Nikon’s competing 105 macro doesn’t have the obstruction on the mount, apparently, as it’s listed by Nikon as officially supporting use with Nikon teleconverters.  [I have not personally verified this]

I have heard, though haven’t verified first-hand, that the Sigma teleconverters do not have the same protrusion, and so will happily mount to any lens on which they fit (i.e. where their front element doesn’t collide with the rear element of the lens).

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