Quote: Why the heck would you buy a $450 18-135 if it has massive vignetting at wide open and f5.6 at 18mm and 50mm, and although it has good center sharpness at 18, the corners are AWFUL! at 24mm it's pretty damn good but from there all of the focal lengths the corners and borders are horrible, at 135 it's off the chart how bad it is.
You are embellishing a bit. I have no use for a lens like the 17-70. It's as simple as that. @ 70, it's fallen out of the excellent range at every F stop. Who knows where that starts? My guess is for the range above 55 mm, you're going to want something sharper. IN that range it has no use, well portarits maybe, a little of that softness won't hurt. At least with the 18-135, it's center sharp... if I center a flower and the rest is bokeh, I'm not even going to notice how soft the edges are. My complaint with the 17-70 is, it's too short for a general purpose walk around lens. I can get a Tamron 17-50 that's both 2.8 and much sharper in the range where.
I take a lot of shots like this....
Does that edge softness make a difference? Not at all because it has excellent center sharpness. The 18-135 has better center sharpness at 135 than the 17-70 has at 70. Look, maybe the 17-70 just matches your style... maybe it's great for you. Maybe the 18-135 matches my style and is great for me. I don't have a problem with that. But as i said, your need to trash the 18-135 is pointless. You don't have to trash another lens to tell someone how much you like yours. Just tell him why you like it and let him make up his own mind.
I use this lens a lot. I think I know how to use it. It's good enough that if you use it to it's strength it's a top notch lens. Do I need to change to my DA*60-250 for landscape shots that need edge sharpness? Of course I do. But I'd be doing the same thing with the 17-70. And the 18-135 gives me excellent center sharpness right to 135mm. That saves a lot of lens changes.