Originally posted by 24thNomad Okay, this helps a LOT. Thank you for that.
Also, I do own the 18-135; I got it with my K-70. When I first got it, I was unsure about it and seemed lackluster. I made myself use it more and will definitely be keeping it. But, I have used it in an indoor concert situation, and the slower aperture is a bane in some lighting situations. Perhaps, I'm not experienced enough to know to how to get around this. But I found it too slow for those settings. In good lighting, though, I definitely agree.
Also, that 50-135 is impressive! That's such nice IQ from a zoom. I'd probably be willing to go past the budget a little bit if a nice copy came my way.
I have never seen a bad copy of the 50-135. I have converted quite a few of them from SDM to Screw Drive and even then the lens is quite lovely. The constant f/2.8 isn't really shown in my picture since it was in good lighting, but I can attest to the fact that it is sharp from wide open. It is an amazing lens for crop - one of the reasons to shoot Pentax APSC.
As for the 18-135 - you are spot on. Good lighting is needed, this is a great walkabout daylight lens and not bad with flash but available light in poor lighting will not sit well unless you are OK with very high ISO shots.