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 Canon DSLRs. What else do you need to know about it?

This lens can be used with a Canon Extender, for those occasions when you're trying to photograh a tiny bird from 100m away. The 1.4x Extender makes it a 420-1120mm f/8 lens which will still retain autofocus when used with a 1D-series camera. The 2x Extender makes it a 600-1600mm f/11 lens which will need to be focussed manually. Insane.

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