The top seven ultrawide lenses

Why SLR lenses only

I am rather disappointed by the review. I know and tried most of the lenses cited, but none of them can rival superwides in Leica M mounts, from Leica itself (18 SE and Tri-Elmar), Zeiss ZM (15-18-21-21C) and Voigtlander (12 and 15 Heliars): near-perfect sharpness from full aperture, simple optical schemes, great flare control and colour. Some of them have incredibly low distortion. I have also to mention that digital is not well suited for demanding superwide shooting. Resolution, vignetting, gamut and sensor artifacts pose severe limits to DSLR output quality, if one is picky on 30 x 45 cm prints or projections.
After wandering in Nikon and Zeiss offering for my D700, I tried a Zeiss Ikon SW with a 15 SW Heliar and never went back: it makes aliasing on the Minolta 5400 II scanner at 103 lp/mm at f/4.5...

Sincerely

Why SLR lenses only?

I am rather disappointed by the review. I know and tried most of the lenses cited, but none of them can rival superwides in Leica M mounts, from Leica itself (18 SE and Tri-Elmar), Zeiss ZM (15-18-21-21C) and Voigtlander (12 and 15 Heliars): near-perfect sharpness from full aperture, simple optical schemes, great flare control and colour. Some of them have incredibly low distortion. I have also to mention that digital is not well suited for demanding superwide shooting. Resolution, vignetting, gamut and sensor artifacts pose severe limits to DSLR output quality, if one is picky on 30 x 45 cm prints or projections.
After wandering in Nikon and Zeiss offering for my D700, I tried a Zeiss Ikon SW with a 15 SW Heliar and never went back: it makes aliasing on the Minolta 5400 II scanner at 103 lp/mm at f/4.5...

Sincerely

Why no RF lenses

The article was concerned with wide angles for current digital systems. DSLR output quality can be better than RF (or mirrorless) quality with conventional, non-retrofocus wide angles simply because a well-designed retrofocus or retrofocus zoom ultrawide will display none of the colour shifts, vignetting or sensor artefacts associated with using Biogon, Hologon or Super Angulon derivatives. Since this article was written, the Sony NEX has given many users a chance to try classic and modern ultrawides on APS-C. For the most part they prove very disappointing even on a format which removes most of their angle benefit.

Had I been writing about wide-angles in a wider context, other formats could have been brought in including medium format digital, rollfilm, and view cameras. It's still hard to beat the classic combination of a 47mm Super Angulon on 6 x 9cm - as found in the Plaubel Proshift, and almost half a century ago in the Brooks Veriwide.

Tokina 11-16 and Pentax

The comment "A Pentax branded variant is made" -- referring to the Tokina 11-16 -- is incorrect. The Tokina is available in Nikon, Sony and Canon mount, not Pentax, and Pentax do not produce an equivalent.