see also:

• Canon EF lenses

• announced in 2015 as part of Canon's plan to finally produce some nice wide angle lenses to compete with Nikon and Olympus
• prior to 2013, their wide angle pro lenses were very average indeed, then it seems they wisely decided to give up on ultra-wide f/2.8 lenses and deliver superb f/4 lenses and thus came their superb Canon EF 16-35mm f/4L IS and Canon TS-E 17mm f/4L tilt shift lens and then this ultra-ultra-wide zoom lens to compete with the Sigma 12-24mm f/4.5-5.6 DG II HSM

• 11-24mm full frame rectilinear zoom giving coverage as wide as 126º diagonal field of view (117.17º horizontal and 95.0º vertical)
• f/4
• 9 circular blades
• close focus 0.28m at 24mm (0.32m at 11mm)
• 16 elements in 11 groups inc 2x CaF2, 1x SUD, 1x UD and 4x aspherical elements
• polycarbonate build
• rear slot in gelatin filters
• weathersealed
• SWC and Air Sphere coatings
• 1180g (2.6lb)
• 108x132mm
• $US2999

• http://petapixel.com/2015/03/02/review-canon-ef-11-24mm-f4l-usm/
  • best at f/8
• http://www.kenrockwell.com/canon/lenses/11-24mm.htm
  • for the first time in Canon history we can get 18-pointed sunstars
  • a magnificent lens.
  • not only is it the world's widest lens, it's also super-sharp and reasonably free from distortion
  • other ultra-ultra wide lenses are not this sharp
  • BUT poor quality lens cap and case!
• http://www.photozone.de/canon_eos_ff/940-canon1124f4
  • 4.5% barrel distortion at 11mm, reducing to 1.8% at 14mm and neglible beyond
  • 3.3EV vignetting at 11mm reducing down to 1.3EV at 24mm
  • very soft edges and corners at 11mm but best at f/8 although centre sharpness has fallen from its peak at f/4
  • considerable CA at 11mm but better controlled from 14mm onwards
  • flare is very well controlled for this type of lens
• https://www.dpreview.com/articles/9071490684/wider-than-wide-a-landscape-photographers-review-of-the-canon-11-24mm - 11mm for Iceland's landscapes and aurorae