Sigma advertise this as the fastest 20mm in the world. Most fixed focal length 20mm’s are f 2.8 - over a stop slower and most zooms covering 20 mm are slower still. So if you need good low light performance from a wide angle this is it.
As you would expect this is not a small lens - it weighs 600g and is finished in Sigma’s speckled matt black EX finish with a nice rubberised focusing grip and a gold ring near the front of the lens. It looks great. Filters are 82mm thread. Sigma - as always - supply an excellent lens hood in the box.
This test is based on the Nikon AF version of the lens but like all Sigma’s it’s available in a wide range of mounts. First impressions are good - at full aperture results with my Nikon bodies were excellent - very slighly soft with barely noticeable darkening in the corners. (that’s with an APS sized sensor so used with film or full frame DSLRs that may be more of a problem) Stopped down sharpness was superb.
However, I also tested with a Fuji S2 Pro body and found a completely different result - stopped down performance was OK just not as good as with the Nikon - but at full aperture even the center was slightly soft - edges very soft. Strange - All I can say is that this lens obviously doesn’t suit Fuji’s sensor.
The lens has quick MF/AF selection by pulling the focus ring back towards the camera for MF forward for AF - and although that seems like a great idea, in practice I found it was the only thing I didn’t like about this lens. The action has a snap to it - it clicks in either location - but it could do with being stiffer to stop it switching accidentally - which I found happening all the time - especially when fitting or removing the lens from the camera.