see also:

• Canon EF lenses

• the very average image quality Canon EF 16-35mm f/2.8L version II was introduced in 2007 this has been updated in Dec 2016 with a mark III version which is sharper wide open at 16mm and with less CA and the 9 blades give much better sunstars but otherwise fairly similar at other focal lengths
• compared to the 16-135mm f/2.8L II lens, the newer Canon EF 16-35mm f/4 L IS is:
  • sharper edge-to-edge
  • less expensive
  • adds image image stabiliser so you can shoot at hand-held at 1/2 to 1/4 second

• announced Dec 2016
• Fully weather-sealed construction
• Sub-wavelength Coatings (SWC) and Air Sphere Coatings (ASC) to eliminate lens flare and ghosting
• Two large-diameter double-surface GMo lenses plus a ground aspherical lens to help decrease distortion, curvature of field and astigmatism
• Two UD lenses help to reduce chromatic aberration
• 9 rounded blades not 7
• 790g (up from 635g in mark II)
• 128 x 89mm
• EW-88D lens hood
• $US2199

• https://www.dpreview.com/reviews/updating-a-classic-canon-16-35mm-f2-8l-iii-lens-review
  • sharpness wide open highest at 16mm (much better than mark II) but 2.6EV vignetting in corners and 2.7% x 0.9% barrel distortion, but lateral CA well controlled and much better than the version II lens
  • at 28-35mm need f/5.6 for maximal sharpness and at these focal lengths, the distortion is pincushion, and the sharpness is only minimally better that the mark II lens
  • distortion similar to mark II lens but simple and easily correctable

• announced 2014
• “by far the best ever from Canon for nature, landscape, interior, real estate, general architecture and outdoor photography” ¹⁾
• 16-35mm zoom
• f/4-f/22
• weathersealed
• 4EV image stabiliser
• close focus to 28cm
• 9 curved blades
• 16 elements / 12 groups
• flourine coatings
• 77mm filter
• 112.8 x 82.8 mm
• 617 g

• announced 2007
• 16-35mm zoom
• f/2.8-f/22
• weathersealed
• close focus to 28cm
• 7 blades and gives great 14-pointed sunstars
• 16 elements / 12 groups
• 82mm filter
• 111.6 x 88.5 mm
• 640 g

From ePhotozine.com's reviews:

	Canon EF 16-35mm f/4 at 16mm	Canon EF 16-35mm f/2.8L II at 16mm
sharpness
chromatic aberration

• despite the Olympus lens is a f/2.8 zoom down to 14mm not 16mm, it is:
  • lighter at 524g instead of 640g
  • shorter at 106mm vs 112mm
  • more affordable at $A1499 compared to $A1899
  • far more versatile as it can zoom out to 14mm in full frame terms
  • focuses closer at 20cm instead of 28cm
  • much sharper wide open edge-to-edge (see charts below)
  • much less CA
  • much less distortion at widest zoom 1.7% compared to 7.4% barrel distortion!!
  • much less vignetting wide open 1.5EV vs 1.9EV
  • both have 7 blades
  • has much nicer star shapes for astrophotographic landscapes of the Milky Way as it has less coma aberration
  • has image stabiliser of 5 stops allowing hand held shots at 1-2 seconds courtesy of the Olympus cameras (the Canon has no IS)
  • has eye detection autofocus for portraits
  • has fast, silent AF for movies
• why would anyone buy the Canon 16-35mm f/2.8 lens then?
  • if you already have a Canon full frame dSLR with 50mp and you shoot landscapes on a tripod at f/8 then it may have a use as it can take filters although you should be buying the much better f/4 lens (although for static scenes, the new Olympus cameras can shoot 40mp HiRes shots with less moire on a tripod)
  • one could argue you can get 2 stops better ISO on full frame, but with this lens you need to stop it down 2 stops to get close the the sharpness of the Olympus lens, so that argument generally won't hold much
  • otherwise see your mental health therapist

From ePhotozine.com's reviews (not totally comparable given different sensor sizes):

	Olympus mZD 7-14mm at 7mm	Canon EF 16-35mm f/2.8L II
sharpness
chromatic aberration

• http://www.photozone.de/canon_eos_ff/877-canon_1635_4is
  • 3.4% barrel at 16mm and 2.1EV vignetting at f/4
• http://www.lenstip.com/411.1-Lens_review-Canon_EF_16-35_mm_f_4L_IS_USM.html
  • nicely controlled coma correction, better than the Nikon 16-35mm f/4G VR
  • astigmatism well controlled at 2.9%

• ePhotozine.com's reviews
• http://www.kenrockwell.com/canon/lenses/16-35mm-ii.htm