You won't believe how big this lens is, even after we've told you that you won't believe how big it is. It's b-i-g. Affectionately known as the "Sigmonster", this is currently the longest lens available for Nikon DSLRs. What else do you need to know about it?

This lens can be used with a Sigma APO Tele Converter, for those occasions when you're trying to photograh a tiny bird from 100m away. The 1.4x TC makes it a 420-1120mm f/8 lens, and the 2x TC makes it a 600-1600mm f/11 lens. Insane. Both combinations will usually need to be focussed manually, though a high-spec camera such as a D3 stands a decent chance of being able to autofocus with the 1.4x TC mounted.

Suggested extra: You might find the Manfrotto MN393 long lens bracket useful when mounting this lens on a monopod or tripod.