Sigma 20mm f/1.8 EX DG
One of the advantages with full frame cameras is the large variety of wide angle lenses. What can you do to make it even better? Make it a large f/1.8 aperture. The question is, how does a 20mm f/1.8 lens stand up on full frame? (For comparison an APS-C camera would need a 14mm f/1.1 lens.)
Build and Handling
The Sigma 20mm f/1.8 is a large lens for a prime. It is built with a nice combination of metal and plastics and has the typical soft touch feel that Sigma lenses have. The EX means it is one of their premium lenses, and the DG means it is optimized for digital full frame.
Although this lens doesn’t have quite the macro capability of its 24mm stablemate, which is 1:2.7, the 20mm does go to 1:4, which still allows you to get very close to your subject, but do realize this lens focus breaths a bit and will be longer focal length at minimum focus v. infinity focus.
The lens uses screw drive focus, so it must be focused manually on the handicapped bodies that don’t offer screw drive. The focus ring is awkward for manual focus, and really isn’t suitable. Stick to AF focus if at all possible. Tiny adjustments in the focus ring change the focus significantly making manual focus difficult to nail. To switch between manual and auto focus you have to slide the focus ring towards the lens mount or push it towards the front of the lens.
The aperture has 9 blades, so even stopped down out of focus specular highlights appear as near circles. The lens also has a aperture ring so it is compatible with older film cameras.
The lens is a 13 element, 11 group design, with a minimum focus distance of 0.20m (7.9 in). The filter threads are large at 82mm and the lens is a rather dense 520g (18.3 oz).
So how does this lens perform on a full frame camera? Read more to find out.