Originally posted by Funsize I don't think my 18-135 was a bad copy. Like I said, I used to really like it; the center was quite sharp and was pretty much always in focus. The problem was pretty much everything that wasn't in the center. This can be used to your advantage, though, because it will help with subject isolation if you're taking a picture of an individual thing. I've got lots of portraits with it that are really nice, but I'm going to need to reshoot every landscape I took with it.
Thats why I gave you an example of an edge image with great edge sharpness. It's a different lens between 20 an 50 mm, than it is between 70-135. That needs to be acknowledged when discussing edge weakness. At 24 mm, it's pretty much the same as the best out there, although I haven't seen results from the 18-35. And as I've pointed out, there are many ways to achieve subject isolation... there is one it's not so good at.... the one that requires wide aperture. But at subject isolation it does just fine in many circumstances...
You don't have to completely obliterate the background to achieve subject isolation.
The 18-35 is a better lens for some things... and it has advantages. I agree. But the 18-135 also has some things going for it to, this is not a slam dunk. The 18-35 is not going to be the best lens every time, unless you have a lot of other lenses to go with it, and you're OK carrying all that weight. In fact, if you don't have a lot to go with it, for most shooters, it's a very limited lens. For the guy who has everything, it's certainly a nice addition to the camera bag.
For most outings I have trouble justifying the weight of my Sigma 8-16, and it covers a focal length not covered by any other lens, so has a unique spot in the lens line up. A lens like the 18-35 overlaps with a lot of different lenses, from the 20-40 to the kit lenses, the 16-50/17-50 etc. It's pretty much only of value to those who feel they have to have the 1.8, in which case, there simply are no other Pentax options.
As soon as he said "Carry in a back pack, with room for one other lens", I ruled it out. Too limited range. Really heavy. Just not that kind of lens.
I'm providing images here, that show exactly what I'm talking about. I'm not sure how there could be a misunderstanding.