Lenses / Re: Canon Camera Museum Posts Technical Reports for EF 16-35 f/4L IS & EF-S 10-18 f/4.5-5.6 IS STM.« on: June 10, 2014, 10:29:06 PM »
Unfortunately I think some are so focused on sharpness and sharpness tests these days, they forget that sharpness is only a piece of the whole pie. There are other elements, such as max aperture, bokeh rendering, flare, color/contrast, focusing ability, falloff, ca, size/weight that are equally important.
thus, I believe some are feeling the 16-35 f/4 IS is a replacement for the f/2.8 II since the former is sharper than the latter. But as you note, it is definitely not a replacement as many would never give up f/2.8 for a bit sharper corners.
Lenses all have a tradeoff, and I wish more would look at the big picture rather than honing in on sharpness above all else. It is important, but many other things are important too.
Sure, but many are using this as a landscape lens, and generally in landscape photography, sharpness is one of the most important things. Let's go through the things you mentioned:
Max Aperture - in general, not so important, except for non-star-trail astrophotography
Bokeh rendering - not important
Flare - by all reports, this lens is better than the 16-35 2.8
Color/contrast - we will see shortly, but I doubt with current technology that this will be worse than the 2.8, and even if so, color is typically added/changed in post
Focusing ability - not so important
Falloff - should have less than a 2.8 lens, but will see shortly
Ca - judging by the elements, should have less than the 2.8
Size/weight - beats the 2.8 by a tiny bit, and is insignificant in my opinion, so I would say they're evenly matched.
So if you're using this for landscape, then the f4 is the way to go my man. Now, of course people us this for other genres, but I'm just going by what the most common usage for the UWAs is. If you're curious how I came to that conclusion, search flickr or any other photo sharing site for photos from the 16-35, 17-40, and 14mm lenses and you'll find that the majority are landscape, followed by architecture.
16-35 II is also hugely popular for weddings and pj work, where f/2.8 is critical as is bokeh quality (especially at 35mm). So, that is the area the f/4 lens would easily be trumped imo - in these applications the important content is near center of the frame, not the corners.
While many will use this as a landscape lens, I think Canon will come out with something even better for landscapers in the future as this lens still does not quite compete with Nikon's 14-24, moreso with the 16-35 f/4 VR. I would argue that 14-24 is a more useful range for landscape than 16-35, plus the Nikon does f/2.8 while remaining sharp across the frame. 16-35 range is very useful to wedding/pj because it works in very cramped spaces while still being able to do 35mm f/2.8 portraits.
Introduce the 16-35 F4 and then after milking the market (esp landscape photographers) drop the 14-24. All the landscape photographers will switch and Canon can make extra $ that way. Good marketing ploy. Unfortunately I need a good landscape lens soon, so I'll spring for the 16-35 F4 and then again for the 14-24 if / when it is available.