Originally posted by NVSteve I'd prefer the best quality from the start. Would you say the 18-55 is the best lens out of the 18-135, 16-50 & any other weather sealed zoom I may have missed? I have seen positive posts about all 3, but I have also seen negative posts about all 3, which is not making my decision any easier.
Check out some of the evaluation data from photozone:
DA 18-55 WR DA 18-135 WR DA* 16-50 WR
At the widest end and wide open, none of them are stellar at the borders or extreme borders (fair to good), but the centres are very good for the 18-55, and excellent for both the 18-135 and the 16-60. If you stop the *16-50 down to the initial aperture range (f/3.5-4) of the other two lenses at the wide end, the borders are "bordering" on very good. Each of the three improves in the borders appreciably at f/5.6 - f/8, and the 18-135 seems to be better here than the 18-55.
The 18-135 pretty much stays ahead of the 18-55 through out the rest of APS-C "normal" to short portrait range 24mm - 50mm. The 18-135 arguably also gives the *16-50 a run for the money at f/4-f/8 through out the rest of the same focal length range. However, the resolution on the borders for the 18-135 seem to drastically reduce on the longer end of the focal range. The *16-50 while giving you a wider aperture at f/2.8, is also quite a bit more expensive, and is 30% heavier than the 18-135.
The DA* 50-135 is weather sealed, and a fantastic lens, however it does not cover the focal range you are looking for, it is very expensive, and it is also larger and 40% heavier than the 18-135. I personally do not own the 18-135 (not yet at least), but if you look at some of the photos that have been taken with it by the K-5, they look very nice. What are you intending to do with your photographs ? As a general "hike-around" lens to capture moments that will be viewed on-line and/or produced in small prints, I am sure it would be very nice. If you are looking for professional-grade results to be put into large prints, you may need to haul more substantial glass and camera stabilization with you for that......