Sigma 20mm f/1.8 EX DG.

When it was released, this prime lens was the largest aperture wide-angle available. Its optical construction is made up of 13 elements in 11 groups with two aspherical elements and 9 aperture blades. The DG version has an extra coating on the rear elements for better flare performance.

Interestingly, it has a minimum focus distance of 0.20m (0.66ft).

Obviously, the combination of shallow depth of field and dome ports when using this lens wide open limits the usefulness of its aperture.

The lens was tested with 30mm of extension and a ZEN 230mm (9”) dome port

Test

Crops are from the corners of the images at 100%.

Full high resolution downloads of the test images are available. Please use the password “wide-angle15”.

Conclusion

This lens test is tough as the lens also had to cope with the foreground of the quarry being pretty close to the dome too. This gives general DOF issues at small apertures, regardless of the dome.

Subjectively, I feel that the corners are acceptable at f8/f9.

This lens has been discontinued by Sigma, but some dealers still have inventory (as of April 2015) and there are pre-owned lenses available.

The lens used for the review is the reviewer’s own.

1. Introduction.
2. Nikon AF-S NIKKOR 14-24mm f/2.8G ED.
3. Nikon AF-S NIKKOR 16-35mm f/4G ED VR.
4. Sigma 20mm f/1.8 EX DG.
5. Nikon AF-S NIKKOR 20mm f/1.8G ED.
6. Tokina 17mm f/3.5 AT-X.
7. Nikon AF-S NIKKOR 17-35mm f/2.8 AF-S Zoom.