Something About Ultra-wide-angle lenses

1. Nikon AF Zoom-Nikkor 18-35mm f/3.5-4.5 D ED IF Aspherical
Nikon's lightest-weight ultrawide zoom, 11 elements in 8 groups, 93mm long, 82,5mm diameter, 77mm filters, 370g, one aspherical lense.
The close focus is 0.33m from the film plane, viewing angle of 100-62°.
The diaphragm has 7 rounded blades, stopping down to f/22, not quite regular in circular contraction.

2.Nikon 12-24mm f/4G IF-ED AF-S DX Zoom-Nikkor
Option for APS-C Nikon DSLRs,  11 elements in 7 groups, 90mm long, 82.5mm of diameter, 485g, 77mm filters, the close focus is 0.3m marked, magnification 1/8.3, on D100 viewing angle 99°-61°, largest aperture F4, Stops down to f/22.


3.Nikon 20mm f/2.8 AF
12 elements in 9 groups, 52mm long, 69mm of diameter, 270g, Stops down to f/22, it focuses as close as 0.25m, 94°of viewing angle, diaphragm has 7 blades.

 4.Nikon AI NIKKOR 24mm f/2s

This was the fastest 24mm lens ever made by Nikon up until 2010.  
11 elements in 10 groups, 51.5mm long, 63mm of diameter, 300g, close focus at 0.3m, max reproduction ratio 1/8.6, viewing angle 84°, 52mm filters, 7 straight blades, stops down to f/22

 5.Nikon AF-NIKKOR 24mm f/2.8 D

 9 elements in 9 groups, 46mm long, 64.5mm of diameter, 270g, 52mm filters, 7 straight blades.

stops down to f/22, close focus at 0.3m, viewing angle 84°.

 6.Canon EF 20-35mm f/3.5-4.5 USM

Canon´s first attempt to provide an ultra-wide lens to the masses.

 12 elements in 11 groups,  69mm long, 83.5mm of diameter, 340g, 77mm filters, close focus at 0.34m, 5 aperture blades, magnification of 1:7.7.

 7.Canon Zoom Lens EF 17-40mm f/4 L USM

12 elements in 9 groups,  96.8mm long, 83.5mm diameter, 475g, 77mm filters, 7 mostly straight blades stopping down to f/22, close focus at 0.28m from the image plane.

 8.Minolta AF 17-35/3.5 G

15 elements in 12 groups, close focus at 0.3m, 77mm filters, 90.5mm long, 82.5mm diameter, 600g, 7 aperture blades, circular, constant maximum aperture of f/3.5.

 9.Sigma 17-35 mm F2.8-F4.0 EX DG HSM

Covers a super-wide angle of view 104 degrees, 15 elements in 14 groups, 86mm long, 89mm diameter, 435g, 82mm filters, minimum focusing distance of 27cm at all focal lengths, maximum Magnification of 1:4.5.

10.Sigma AF 15-30mm f/3.5-4.5 EX DG

 17 elements in 13 groups, 130mm long, 87mm diameter, 615g, close focus at 0.3m, angle of view: 110.5-71.6°, 8 diaphragm blades, max magnification 1/6.