Fisheye lenses aren’t like ordinary wide-angles. For a start, their angle of view is wider (a full 180 degrees on a Nikon DSLR) and second they don’t attempt to correct straight lines, rendering them instead as curves. These two factors produce distinctive and highly odd renditions of the world.

In fact, this is not the ‘widest’ Sigma fisheye. There’s also a 4.5mm ‘circular’ fisheye which, unlike this one, doesn’t even attempt to produce a rectangular image, generating instead a round picture with an even wider angle of view than this one (we’ll look at this in the next issue).

The extra-wide angle of view means some odd design features. The front element of the lens protrudes to such an extent that a special ‘deep’ lenscap is provided. This also allows space for the fixed ‘petal’ lens hood. These are essential on a lens this wide because with this angle of view on a sunny day, the sun will always be either in the frame or not far outside it.

The Sigma’s a little fatter and shorter than the average kit zoom, not to mention a

good deal heavier. There’s clearly a lot of glass and metal crammed into a small volume, but it does feel very well-made as a result. The focusing is fast and quiet, too – not that you’ll need it very much, because with a lens this wide, most of the things you’ll photograph will be practically at ‘infinity’ anyway. It will focus right down to 13.5cm, though, which is an advantage where you want to produce striking perspectives and distorted relationships between nearby objects and their backgrounds.

Optically, the performance is very good. Definition in the centre of the frame is fine, and while it does drop off towards the edges, where there’s also some colour fringing. This kind of evaluation is largely academic, given the wildly distorted view of the world you’re capturing in the first place.

Depending on what you’re photographing, the distortion may or may not be apparent. Straight lines running through the centre of the frame are largely unaffected, but those near the edges are bowed outwards. This shows up most when the horizon is positioned close to the top or bottom of the frame and when you have any buildings in the shot. You can control the strength of the distortion to some degree by carefully adjusting your viewpoint and the way the shot is framed.

So who needs a lens like this? It’s a pretty extravagant purchase for an amateur photographer, since it’s really a special effects tool that only does one thing. If you love the effect, though, or if you’re a professional looking for a way to tempt clients with something a little different, it could be a good buy. This kind of lens can be useful in scientific environments too, for example when measuring cloud cover.

If you’re actually looking for a standard ‘rectilinear’ wide-angle (ie, straight edges to come out straight) you need Sigma’s 10-20mm wide-angle zoom instead. But be warned – compared to this, it will look rather tame…

Final Verdict It’s a lot to pay for a lens that is essentially a ‘one-trick pony’, but this Sigma 10mm fisheye is still worth considering for photography fans that want to try something different OVERALL

Our lens reviewer, and technical expert, Rod is a veritable photographic encyclopaedia. His illustrious CV has seen him write for many mags, websites and journals.