[Brightcolours]

the corners at17mm of the 17-40 are terrible.

Especially wide open. Stopped down past f8, they kinda are ok. 

[toni-a]

Well at least my tokina sample is very satisfactory even at the corners at f2.8 but it's very heavy impractical for hiking with a fragile protruding front element. I learnt the expensive way that image quality isn't everything

[Rover]

the corners at17mm of the 17-40 are terrible.

At 17mm, yes - that's why that lens is so cheap - but a lot better at the longer focal lengths, even at 20mm (somewhat). The 17-40 seems to have very little of the wacky field curvature issues of the 20/2.8 (that really seem to drive the resolution into the ground unless you carefully manage the subject distance) and similar vignetting at comparable apertures (way less than what the 20 has wide open). Plus you get the versatility of a zoom, weather sealing and better build quality for a sum that isn't radically greater. The used prices are usually good because the 17-40 is a "starter" zoom and a lot of people were getting it as such but offloading it later in favour of the 16-35/2.8 and whatnot.

 

Well, *personally* I wouldn't have bothered with the 17-40 either - I was scared by the very Photozone review that indicated miserable corner sharpness at 17mm, even though I was never a FF user. That, and I wanted more speed at that time, so I went with the 17-35/2.8 L and then with the 16-35/2.8 L II. Now, of course, I couldn't care less about the 2.8 aperture (well, mostly) so I chose the 16-35/4 L IS. I can sing more praises to it... again and again.

[Polkaha]

Look at this picture, taken from a distance of ca. 3meter. The picture has been perspectively corrected by Lightroom, that is why you see the two white triangles at the bottom corners.

https://www.dropbox.com/s/nqoa54qj7j3xag...7.jpg?dl=0

Aperture was at f/.6.3.

I can only have positive feelings on the quality of this image.

 

Hans

[JJ_SO]

If you're not distracted by the sharpness in the center and the blurred edges, then I don't want to take your positive feelings away.

 



 

Edit

After second thought: If you really were only 3 m away from the facade, it might as well be the DoF was just not enough - and some blurr will also go to the account of massive perspective correction, so I think I should not blame the lens for all what I see.

[Rover]

Sorry, the borders (not the corners) look pretty meh regardless. JoJu has summed it up pretty nicely. And yes, I would've stopped down to kingdom come for such a shot - though I'm not sure it's a DOF issue (I did get unsharp sides of a flat facade from the slight tilt when shooting with a 70-300 lens at 220ish mm, but would not have expected this issue to be noticeable at 20mm).